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).