A moebus strip.
It is called the profile
The far side.
Pennies have Abraham Lincoln's face on one side. Nickels have Thomas Jefferson on one side. Dimes have Franklin Delano Roosevelt's face on one side. Quarters have Georges Washington's face on them. Half-dollar pieces have John F. Kennedy's face on one side.
To answer this question more details need to be provided. For example one a 3D shape one side is called a face.
bilaterally symmetrical
An edge.
no shape
A sphere
A blob.
a line
A Moebus strip.