Orientable:

The orientable surfaces are the sphere, the torus, and the tori of higher genus. In more generality, these are called the sphere with n handles (where n may be zero).

The orientable surfaces all have even Euler Characteristic.

Every orientable surface can be embedded in three-space. An orientable surface mapped into a Euclidean space will have two distinct sides.

See also:

Non-orientable surfaces