Behaviour is quite literally everything that we do! From the mundane to the extreme, all behaviour has a function, purpose and is ultimately a form of communication. This is especially true for challenging behaviours.
There are a multitude of factors that influence behaviour, including different environments, social settings, personal skills, frustration tolerance… the list can go on an on. All these different influences make it essential to look at behaviour holistically and not just focus on x+y=z.