You may be chatting with Mark.... or maybe a bot emulating Mark. It is up to you to decide and it could be either at any given time! My own version of the Turing Test, in fact, it is the first real web-based Turing Test.
A chat bot is a humanlike conversational character.
Its conversational skills and other humanlike behaviour is simulated through artificial intelligence.
It often acts as a virtual assistant and it can have its own visualisation through an avatar
or it is faceless. We expect that through the years every conversational chat bot will grow into a real virtual human.