if you mean uh, um, er, and so on, these disfluencies are commonly referred to as filler words, or fillers. there are other sorts of discourse markers such as "oh", "well", "now", "then", and "I mean" and discourse particles such as "you know" and "like" which may also be referred to as fillers.

maybe jim, our resident linguist, will drop by and clarify these usages.