A typical Kundalini Yoga class 'as taught by Yogi Bhajan' looks like this:

Length of class:	90 minutes
Tuning In:	To focus the attention and to bring the focus inwards (3x Adi Mantra Mantra & 3x Mangala Charn Mantra)
Warm Up:	Exercises to flexibilize the spine plus general warming up exercises
Kriya:	Kriya Exercise Set with a specific theme
Deep Relaxation:	Approximately 10 minutes
Meditation:	Either Pranayama or Mantra Meditation with a specific focus (usually between 5 and 11 minutes)
Tuning Out:	To close the class with the 'Long Time Sun'-Song followed by 3x 'Satnam'

 

Kriya means 'action'. It is a set of exercises, usually between 5-8 different exercises/postures in combination with specific pranayama, focus, bhandas (locks), mudras & mantras, in a specific order designed to produce a specific effect. 

Kriyas all have themes, target different areas to specifically benefit from the exercise. Kriyas can focus for example on the physical organs, the glandular system being the guardians of our health, the nervous system. Others specifically aim at raising awareness levels, sharpening intuition, elevating consciousness, thereby teaching us the tools to deal with life's challenges and helping us to experience harmony in body, mind and soul.