Discourse Marker
A word or a phrase which is linked weakly or not at all to an adjoining sentence and which serves to keep a conversation or a text flowing smoothly.
Discourse markers show the connection between what a speaker is saying and what has already been said or what is going to be said; they can help to make clear the structure of what is being said; they can indicate what speakers think about what they are saying or what others have said.
There are a very large number of discourse markers. Among the items commonly used are yes, so, of course, nevertheless, on the other hand, frankly and well.