If there are 2 moves linked, that means that those two moves will be used one after the other BEFORE the other team has a chance to attack.
If there are 3 moves linked that means that those three moves will be used one after another after another. And the same for four moves
When you used a linked move, it takes PP away from all moves that are linked together. SO if I used a linked Leer and Pund, it would take 1 pp away from both. of course, if I was battling a pokemon with Pressure, it would take away 2 from both.
Also, if I was versing a ghost pokemon, the Leer would work but the pound would only do 1 damage as Normal does not effect ghosts. It would be the same with dusclops, only it would take away 2 PP from both.
You can only link moves by a link box found in dungeons, or from Gulpin in Pokemon Square for a fee of 150 poke
Hope I helped!
;000; MM ;000;