Most 'real' trucks (unlike cars and car-like SUV's) use body on frame construction rather than a unibody. So, the body & frame are two separate units that are bolted together with rubber or polyurethane isolating bushings in between. A body lift in simplest form is just a set of spacers (and longer bolts) that extend the gap between the two. It's just cheap clearance for larger tires and like everything else has it up & down sides and can be overdone. A suspension lift is basically just a set of 'taller' springs (longer coils in the case of a TJ, leaf springs with more arch in the case of a CJ or YJ) that raises the frame further up away from the axles creating more room for bigger tires. Plusses & minuses there as well as well as different quality of springs and spring rates which will effect ride, handling & flex.
'86 CJ-7 Laredo: 4.2,T-999,D300,D30/D44,'94 YJ tub, full cage, Shrockworks rockers, OYR corners, AC,cruise,restored seats,3 tops,2.5" Superlift,F-T shackle reversal, RS9000x's,35" Dunlop Mud Rovers.
'83 Scrambler: time & money pit under construction with parts from CJ's,YJ's,TJ's,FSJ's,GM,Ford,IH,Honda,Toyota and a whole lotta aftermarket & custom stuff.