A sphere
A blob.
a line
A Moebus strip.
It is a face.
Mobius strip
To answer this question more details need to be provided. For example one a 3D shape one side is called a face.
A face value in maths is the out-side of the shape, as to say the face of a shape. The face value is the sides of a shape.
The side
The faces in a 3-D shape (polyhedron, for example) are bordered by edges.
They both have a face, not a :) face but a side of a shape is called a face and a 2d and 3d shape both show a face of the shape
A circle comes to mind as the face of a right cylinder (which has 2 faces). The curved side is not considered a face.