balcar
+1y
2 links are just to bars that come back that is welded or clamped to the axle, causing the axle to swing/rotate wtih the bar.
3 link normally consists of 2 lower bars that come straight back, and one on top, they all pivot on the frame and on the axle to help keep your pinion correct, the upper bar is also triangulated to keep the axle from shifting side 2 side.
4 links, parrallel and triangulated, 2 lower bars that pivot and 2 upper ones that pivot on both sides as well, the uppers can be triangulated or parrallel with the lowers. If they are parallel with the lowers a panhard bar or a watts link is needed to keep the axle from swaying side 2 side.
5 links, normally a 3 link with 2 extra bars one end with a shackle to install a air spring or coil onto.
6 link same as a 5 link exept with a 4 link.
5 and 6 links are great if you don't have enough width to install your air spring/coil on your bars, which gives you a nicer ride.
I've been up since yesterday afternoon so i'm tired, forgive me if I didn't make since anywhere or misspelled anything. Heck i'd misspell shit when i'm not tired, so never mind.