Take for example the battle pet GRO (2 mana 2/4, grows +1/+1 every turn). Being a high-stat card in itself and a scaling threat — getting big every turn, the primary thought would be just to remove it immediately, find a way to trade efficiently using your minions or use removal. On a particular circumstance, especially when playing from behind, there might be a better way of dealing with it. Instead of using cards to remove it, you can just apply tokens to block its path and allow it to attack the token. Being a battle pet, it is effectively “stunned”, making it all in all useless despite its humongous stats. That is the main concept of kiting.

This may better be explained by a sample interaction. Take note of 3:20 where kiting begins.

Kiting all the way

The main point would simply be, given a threat, instead of thinking mainly on killing the threat via trading or using a removal, be aware of kiting as a possibility.