it would be even harder to explain with a video i guess, i'll try to explain it from the technical standpoint.
the "tick" unit is the smallest unit in a module. it derives from the screenmode that the old Amiga machines used and i think it's 60hz. So 60hz is the smallest unit you can get. Based on this unit, you have "rows" in your modules. A row has 6 ticks as a standard value in all trackers (you can see that for example in modplug tracker in the toolbar, it should display something like "Ticks / Row: 6"). this internal division is there to scale sliding effects (volume slides, pitch slides and all the jazz). so if you set the Tick/Row to 3, one row is half as accurate when it comes to sliding (e.g. it will slide only half a note down instead of a whole if you're using a "portamento down" effect"), but it will also be double speed. now we come to the beats. The standard BPM rate in any module is 125 BPM and you get those if you put a beat on every 4th row. So every 2nd row is 1/8 and every row is a 1/16. If you use only 3 ticks/row, this will split up further: Every 8th row is a beat, every 4th row is 1/8, every 2nd row is 1/16 and every row is 1/32 (you should know that from music theory).
