No, convertibles doesn't suggest that you should be getting your little one a corvette, nor even saving for one for that ever-important driving age... which every parent hopes is very, very far away!
Convertible cribs are often a standard among those sold at discount retailers. Since you're usually shopping in stores like that for the value factor, a convertible crib makes sense for them to offer because it provides you with the ability to convert the baby crib to a baby bed as your little one grows.
A convertible crib can usually be switched into 2 other forms as your child grows: a day bed or a toddler bed. Usually a toddler bed conversion will require the purchase of a separate kit, so make sure that you understand in advance that you're not completely clear of purchasing bedding for your growing child. Some convertible cribs have even added a conversion ability to a full size bed.