Ask a hundred yoga devotees, and you'll get a hundred different answers. But most will agree that yoga in the modern world is having a bit of an identity crisis.

At one end of the spectrum, it's an ancient system of physical and spiritual discipline, with its origins in the Indus Valley perhaps as long as 5000 years ago. At the other, it's a multi-million pound industry, a wellbeing cliché that's used to sell everything from probiotic yogurts to cashmere hotpants.

Yesterday I saw a poster advertising “BoxingYoga™" – just the latest of many attempts to stake a claim in what has become a branding goldrush. As Brand Yoga grows more and more commercialised, many yoga students find themselves searching anxiously for an 'authentic' yoga experience.

So, what is Yoga?

The problem is there's no such thing as a typical yoga class - or a typical student. Watch the hard-bodied athletes powering through an advanced Ashtanga workout, and you might struggle to see what  they have in common with the smiling pensioners gently surrendering to gravity in a Scaravelli-inspired session, or the roomful of bright-eyed, mantra-chanting Kundalini babes - yet these are just three of the many things we call 'yoga classes'.

With such a vast range of options available, how can you find your path through the yoga jungle? Is there any way to tell if you're doing the right kind of yoga? The 'real' kind, the kind that works? In other words: are you on the road to enlightenment, or just jumping around for a bit, then lying down?

Here on, we will be running through the different forms of yoga out there to leave you with a comprehensive guide, steering you through some of the jargon and demystifying the main styles of yoga commonly taught in the UK today. Since the beginning, various practitioners have claimed health benefits for their particular style of yoga that range from reduced back pain and better moods, to ecstatic sexual experiences – and even immortality. I'll outline what results you can realistically expect – and how much effort it will take to achieve them!

Defining 'yoga'

First, a few basics. The word yoga comes from the Sanskrit root yuj, meaning a yoke. Sanskrit is a religious language with magical properties: the words really matter, and it's worth thinking hard about what they mean. We could talk about yoga as the 'yoking' or joining together of mind and body. In most styles of physical yoga, breathing is key: by synchronising the breath with the physical movement of the body, the breath acts as a conduit between mind and body, bringing intention into harmony with action.

We could also see yoga as the yoking or harnessing of certain energetic forces within the person. In the Bhagavad Gita (a key text for Hindus and the wider yoga community) the human mind is compared to a horse which must be trained and mastered by the charioteer. His aim is not to conquer the horse utterly, but to form a partnership with it so that it does what he asks. That's the sort of yoke that yoga implies: a pressing into service of all the internal powers at one's disposal by means of steady, long-term training.

Why practice yoga?

The word yoga also carries the sense of a way or path, a bit like the tao in Chinese philosophy. I had a real lightbulb moment when I discovered this, because it freed me up to see yoga as a 'way of doing' rather than a 'thing to do'; as an attitude towards the world, rather than a rigid set of practices. The goal of yoga is always moksha: liberation from suffering. For a devout Hindu yogi that means that when the body dies, the soul is freed from the endless wheel of reincarnation. For me that means a sense of being at one with myself; being grounded and comfortable in my skin; a certain inner calm.

One of the oldest surviving “how to" manuals for yogis is the Hatha Yoga Pradipika, a 15th century Sanskrit text belonging to a secretive, forest-dwelling monastic sect. It instructs the adept in the proper performance of 16 asanas: physical postures designed to purify the body and channel the energies it contains. It goes on to describe various breathing practices, energetic techniques and cleansing rituals with the same aim. All of these are steps designed to prepare the student for long periods of meditation; the whole package has the ultimate aim of gaining extraordinary powers of physical and mental control, and liberation from the limitations of physical existence.

The postures (asana) we practice in most yoga classes in the West today are the distant descendents of this ancient spiritual training system. We still value them for their 'purifying' effects on the body – but the more mystical aspects of classical hatha yoga have largely fallen away. Many people will attend hundreds of yoga classes without ever hearing about meditation, and without realising that some of the shapes they are making with their bodies were originally part of a religious practice. In that sense, we are dealing with a drastically narrowed-down view of the whole yoga picture – even though there are so many different yoga 'brands' for us to choose from.

Finding the real thing

You'll find plenty of commentators complaining that reducing yoga to just another gym-based fitness class sucks the soul out of it. In 15th century India, the original hatha yogis lived in celibate seclusion in their huts in the forest, standing on their heads for hours on end in pursuit of enlightenment. It's more difficult to imagine reaching nirvana at the gym on a Tuesday night in October, with the muffled thud of Abs, Bums 'n' Tums leaking in from the studio next door.

But I don't think it follows that what we do in gyms up and down the country today is 'not really yoga'. Let's not forget that the forest yogis also drank their own urine, shunned the company of women, and were regarded as dangerous cultists by the general public.

Modern yoga has had to adapt to survive in a secular, capitalist society; we've moulded it to accommodate our cultural values. Far from the secret, all-male cult of medieval India, yoga in the UK today is dominated by women, recommended by GPs and taught in primary schools. Appeals to 'authenticity' in this context are almost meaningless.

Here's my suggestion: if yoga is a way of doing, an attitude to the world, why can't we do it anywhere? Couldn't the magic happen in a dusty church hall – or a sweaty gym for that matter?  Some of the most sincere spiritual enquirers amongst my yoga friends started out as gym bunnies, chasing the endorphin high of tough physical exercise. And I've taught students with very low levels of physical fitness who 'get it' almost immediately, despite not being able to hold any of the postures. I say, let the people find the yoga where they can. Or, when I'm feeling mystical, let the yoga find the people - wherever they try to hide.

As the Hatha Yoga Pradipika tells us, success in yoga cannot be obtained by reading books about yoga, adopting a special way of dressing, or telling stories about yoga. “Practice alone is the means to success. This is true, there is no doubt." From that point of view, the important thing is not so much what you practice, where or even how you practice, but that you practice.

In the end whatever works for you – whatever you feel motivated to stick at, and practice regularly – is the 'right' kind of yoga. Yoga philosophy holds that the core of your being is pure and perfect, although darkened and obscured by the world's influences.

The path of yoga is one of uncovering, finding a way back to that blissful state we all hold within us. Ultimately, each of us has the potential to become our own teacher and develop our own yoga practice. So take comfort from the knowledge that the perfect yoga class is destined always to elude you; but while you're searching, your inner yogi might just meet you halfway.