Plywood structure is core with face and back veneer. As wood is from nature which is totally impossible to control so the appearance of the face and back varies.
As a matter of it, there are grades of face & back which are divided into 4, there are A, B, C and D.
It is much easier to get general looking with attached pictures.
Anyway, among them, A is the best quality which is also the most costly, and D is the least expensive.
A-Grade veneer with a smooth/sanded surface and has no knots. Any defects have been repaired with synthetic filler, so they can be painted. Plywood of this grade is ideal for furniture making or cabinet doors.
B-Grade is also with smooth/sanded surface but may have defects which is being repaired and up to 1-inch across.
C-Grade is not being sanded. It may have minor defects that will need to be repaired with knots up to 1 1/2 inches across, discolouration and sanding defects. For the usage of not requiring a high-grade appearance such as for subfloor/inner wall making/garages, C grade can be a choice.
D-Grade is unsanded too with defects that are not being repaired and knot holes up to 2 1/2 inches across, discoloration/sanding defects.
It is also possible that you may also find grades with two-letter classifications, such as BC. BC-grade is mixed grade plywood with one side graded a B, while the other side a C.
