Plywood is a composition of wood veneers (called plies) and glue (or binder).
It is made to be as strong as possible. However, it has a lot of knots and roughness and will take a lot of work to make it look good in a project.
Sanded plywood or softwood plywood is made up of two outer plies that are sanded during the manufacturing process. This makes a great, uniform surface that can be readily painted like this DIY desk.
Hardwood plywood, also called cabinet grade plywood, has a core of regular veneer plies, with two outer surfaces veneered with hardwood for great-looking projects. Walnut plywood, Maple plywood, and Birch plywood are examples.
The cons of this material are that it is expensive and much harder to find in typical hardware stores. If you are making patterned plywood, you definitely want to use this!