Yoga is a system of physical, mental and spiritual development that originated in India over 5000 years ago and is currently practiced by over 450,000 people in the UK alone. The word yoga comes from the Sanskrit word meaning 'union' and is generally used to describe the union of mind, body and spirit. In the West, it commonly describes the physical practice of exercises to prepare body and mind, but this is really just the tip of the iceberg.
Everyone can practic yoga, regardless of age, ability or creed. People come to yoga for a wide variety of reasons; to keep the body strong and supple, to lift their energy, to relieve specific conditions, to heal a 'bad back', to relax more easily, sleep better, to help with concentration and many other reasons.
Some people like to have their own 'sticky' mat, blanket and sometimes blocks, but yoga can also be practised quite easily using a roll mat, sleeping bag and jumpers for padding, making it easy to practice when travelling.
It is best to practice on a relatively empty stomach - I recommend 2 hours after light food and 3-4 hours after a heavier meal. It is important to keep well hydrated too.