Triolies are 3 stokes every quarter note.
I`ll explain it with the timeline picture I used last lesson.
The blue dots represend a strike
The first strike is at exactly 0 seconds, it starts the counting
The forth strike is already a new quarter, that means you start counting to 10 again from zero.
I hope you got it right, it is pretty hard to explain it through writing, if you have any questions feel free to comment and ask (:
Next lesson I`ll teach you how to read notes, And than we`ll get to some real drumming (: