There are a lot of different types and varieties of camellias, but the more common types offered for sale generally fall into three categories:
1) Japonicas - These generally have large, glossy leaves. Most bloom in late winter or early spring, and the entire bloom falls off instead of petal by petal. Most of the time, these grow larger than the sasanquas.
|A japonica bloom from early last spring.
2) Sasanquas - Usually with smaller leaves, these generally bloom in fall or early winter, and their blooms fall petal by petal.
This is how I remember the differences:
See them first (bloom earlier)
Sun tolerant (more than japonicas)
|Sasanqua blooms from this fall.
The third common type of camellia is the Sinensis. I personally don't have any of these, but they are intriguing because tea can be made from their leaves.
Camellias can grow as tall as a tree or short and wide, so it's nice to do a little research before purchasing (or go to a good nursery where they will help answer your questions). Some camellias can take quite a bit of sun, others like it very shady. Roses like to be planted deep; camellias like to be planted shallow.
When looking around my garden for a good spot to grow camellias, I consult my "cheat sheet":
Would a hydrangea grow there? If so, then it's probably a good place for a camellia.
And don't forget - camellias can make great potted plants, too (so you really don't have to move to enjoy one)!
Want more information? Check out the American Camellia Society's website. You'll be thrilled to know they are working on more cold tolerant varieties, as well as camellias that bloom year round!