I dont know if any of this is right because i havent actually ever used a metronome but i can tell you what i have heard.

right, there is 4 beats per measure in 4/4 time. 1 2 3 4 like that.

So, if you play one note per beat, thats a quater note.

If you play one note for the duration of the four beats (hold it) thats a whole note.

Now, if you play 8 notes note in the duration of 4 clicks (two notes per click) they are 8th notes.

And then if you play 4 notes per click (16 notes in a measure of 4 clicks) then they are 16th notes.

There might be more to it, but this is what i know.