What is Entity?
As the definition goes, it is the variable element of Intent that we intend to Parameterize to allow input of different Values. In other words, its the input value(s) in the a sentence while communicating with bot, that we pass to the bot, based on which we seek outcome(s). You can use this value then, to may be invoking a REST call to fetch the result. A bot will first resolve the Intent and then resolve the Entity associated to that Intent.