A breech delivery is any delivery in which the baby is not delivered with the "standard", head-first, presentation.
There are different types of breech presentations:
The frank breech presentation is when the bottom presents first, and the feet and legs are stretched up toward the head.
The complete breech presentation is when the bottom presents first, and the knees are bent, with the feet down near the buttocks (rather than straight up and near the head).
The footling breech presentation is when the feet present first.
Frank breech babies can be delivered without C-section, depending on the circumstances. It is common, however, for C-section to be recommended in breech presentations.
On a personal note, my 34-week premie was a "frank breech baby" and was delivered without C-section in about an hour and a half.