[kisito]

Words like "you know" , "Um' "Uh" are often used as conversation fillers. A filler is usually a word or two that is meant to give the speaker time to assemble his or her thoughts before speaking. They don't usually mean much.
We have others like "Well" especially used when stating an opinion after a question is asked.
Fillers simply buy us a bit of time. And they exist in all the four languages I speak - French, English, Chinese & West African Pidgin English. I guess they do in every language.