There are a few different lift systems out there, Coleman & Jayco use their own systems, other manufactures like Rockwood, Viking, ect use a system made by Goshen or L&W.  Some use a system of cables, blocks, & Springs while others just use a system with cables & pulleys.

Here's a link to Coleman's lift system guide available here on Canvas Campers, it should give you a better idea of the basics of how they function.