Recumbent Stationary Bike

Upright exercise bikes with great value like schwinn airdyne exercise bike, stationary exercise bike

Do you just start pedaling to turn on a recumbent stationary bike ?
if it has an " on" switch, where would it be at ?

Is there any difference between an upright and recumbent stationary bike?
Do they give different results or anything?

Recumbent stationary bike or Upright stationary bike?
Which is better??I'm not worried about space