Plywood is a versatile wood product with applications ranging from woodworking to home building. Manufacturers shave thin wood layers, called veneers, from logs. They flatten and grade the veneers, then glue them together in a process that uses heat and pressure. Different types of plywood have different grades and specifications that indicate their allowable use, appearance and strength.
No, you cannot just pick up any piece of plywood to construct whatever you want. It is available in different sizes and thicknesses, and different types are used for different purposes. Here's a complete guide on the different sizes of plywood, and the types it comes in.