Different parts of a Rubik's cube
Edge - 2 colours
Therefore you should always think of it as a red and white piece, instead of separately as the colours red and white.
Corner - 3 colours
Another thing you need to know is the difference between these two:
A face
A layer
Source: https://rubiks.com/uploads/general_content/Rubiks_cube_3x3_solution-en.pdf