We use you know very commonly in speaking. It is used to check with our listeners that we share the same knowledge. When we use you know, we assume that the listener or listeners do have the knowledge that we want them to have:
Well, what can I say, you know, I want my career to go far.
A:How was the match?
B:Well, they played OK but the defence was, you know, the same as always.
You know is also sometimes used to allow us time to think when we are speaking:
A:Did you like the play?
B:Well, I’m not sure, it was, you know, it was interesting.
