What does a rectangular prism look like?

Answer 1

Think of it as a box, and to make an easier name, call it "cube". It has 6 faces, 8 vertices [or points], and 12 edges.

It looks like a 3D rectangle.

* * * * *

Do not call it a cube because it is not a cube. A cube has all its sides of the same length whereas a rectangular prism does not. It is called a cuboid to indicate that it is like a cube but not quite the same thing.
A cuboid

Answer 2

it is a 3D rectangular rectangle