Kickback can occur when the chain’s teeth catch on something as they rotate around the tip of the blade or if the wood closes and pinches the bar it. (This can often occur with very fresh, new wood).
There is a 'kickback zone' on a chainsaw bar. The image below shows the area. You should avoid using this part of the guide bar when cutting.
Kickback is almost impossible to control manually and will throw the bar and chain back and up in an arc towards the operator, but there are a number of safety features which can prevent or reduce the instances of kickback. (See 'What safety features should I look for on a chainsaw?')
The danger can also be significantly reduced by making sure you are not directly behind the chainsaw during operation. (See 'The dos and don'ts of chainsaw use')