What is the difference between a toddler bed and a twin bed?

A toddler bed is essentially a crib without the front panel or "footboard" of the crib. Instead, there is a panel or rail which is lower on one end and allows the toddler to climb in but prevents him/her from rolling out of the bed when sleeping. Most of the better cribs can convert from crib to toddler bed and some can even later convert to a full bed. Just use google images and type in toddler bed and you'll get lots of pics to look at to get a better idea of the difference.