if I remember correctly, in my time at school we used to call them temporal conjunctions. The simplest conjunction is "and". It links two sentences of equal "value". Certain conjunctions join two sentences of which one is the main, "leading" one, the other one expresses something which defines the first sentence. E.g. I read a book (before I went out). I read a book makes perfect sense on its own. Before I went out merely defines it a bit more, but it would not stand on its own. Before links the two, and tells us that it is going to tell us something about time: one action happened before the other one. I agree that it is quite sadistic to teach eight year olds this kind of thing. I was the same age too!