Recumbent exercise bikes are great for people who need a large seat or extra back support. They often have an easier step-through which helps those who may have mobility issues.
Recumbent bikes work more muscles and are easier on the lower back than upright bikes or spin bikes. They work more of the glute muscles (bum) than upright bikes. You can even do an upper body workout with dumbbells or similar while peddling for a total body work out.