Most of them quote a number in inches , which is anathema to a sizeable proportion of the world's population. Tell me this makes sense. Tandem Two riders in line Sociable Two riders side by side Steering ASS Above-seat steering. Need not be physically above the seat, just generally at a greater altitude. USS Under-seat steering.
Handlebars are sort of below or beside the rider.
May be connected directly to the fork, or by a linkage. Need not necessarily be under the seat as such. Stands for Over-seat steering, means the same. RWS Rear-wheel steering. Found on some trikes.