Staples generally come in a same structure: simply a formed metal wire bent into a very precise U-shape. It comprises 3 parts: the crown, the legs, and the point.
The part across the top is called the crown. It determines what will drive the fastening tool as different tools require different crown sizes.
The 2 legs are parallel and are designed to penetrate into materials. Length of the leg varies as the application changes. Each tool will generally drive a range of different lengths.
Tip of each leg is known as the point. They normally come as chisel points, with high holding power needed. The points may be divergent. Besides, they have been specially treated to guide the legs in a curve rather than straight down into materials. It would be much harder to pull the staple out if the legs are not parallel.
Crown staples can be coated with different materials. Typical examples are stainless steel staples and galvanized steel staples.