Traditionally, trampolines have a net or bouncing net that is attached to springs that will stretch when you bounce on the net and then rebound to give you the desired effect. These springs can at times catch you or your clothing and lead to injuries and accidents.
A springless trampoline, on the other hand, does not have such springs and this makes them safer to use. They will have a rod that is under the rim of the area where you jump. These rods get flexed under the pressure created by the user and when combined with the flex of the jump give the user of the trampoline the needed bounce. Other trampolines that are springless will have elastic bands instead of the traditional coil springs. These bands are made of a thick material that is not easy to stretch by hand.