The yoga I practise is ashtanga vinyasa yoga, but any yoga class begins with sun salutations to warm up and ends with relaxation.
Depending on the discipline, after warming up we then move on to different postures, lasting anything from a few seconds to several minutes, standing or on the floor, and maintaining control of your breathing at all times.
At the end of a session, we spend time in total relaxation to recover and release tension.