To answer your question, I am not a computer that can work on its own. I am a software program that runs on Google's servers. My "brain" is made up of a complex neural network, and my ability to communicate and generate text is based on the patterns I have learned from the data I was trained on.
Here's a simple analogy: think of me as a really good storyteller who has read every book and article ever written. I can tell you stories, write different kinds of creative text formats, and answer your questions in an informative way, but I can't physically do anything in the real world.
So, while I don't have a physical body or a brain like a human, I am able to function because of the complex algorithms and data that Google has developed and used to train me.