A plywood saw is a saw

Saw

A saw is a tool that uses a hard blade or wire with an abrasive edge to cut through softer materials. The cutting edge of a saw is either a serrated blade or an abrasive...

 that has a fine-toothed blade that minimizes tearing of the outer plies of a sheet of plywood

Plywood

Plywood is a type of manufactured timber made from thin sheets of wood veneer. It is one of the most widely used wood products. It is flexible, inexpensive, workable, re-usable, and can usually be locally manufactured...

. An extra set of teeth on the curved upper edge of the blade allows starting of a cut on the inside of a panel (away from the edge) without having to drill a starting hole. The standard plywood saw blade is 11 inches long and has 14 tpi (teeth per inch).