One of the first auctions that I attended, I found out that there are different types of plates when it comes to a set of dishes.  Here are some of the more popular ones that you will run across:

Dinner Plates—they are flat and usually round (there are other shapes like square out there).  Dinner plates range in size from 9 ¾ inches to 11 inches in diameter.

Salad Plate—these are also known as a side plate.  They are flat and usually round and range in size from 7 ¾ inches to 8 ¾ inches in diameter.

Bread & Butter Plate—these are also known as a dessert plate or even a cake plate.  Like salad plate, this type of plate is flat and usually round.  They range in size from 6 inches to 7 ¾ inches in diameter.

Luncheon Plate—they are often confused with the dinner or salad plates.  Luncheon plates are flat and usually round, ranges from 9” to 9 3/4” in diameter.

This is only a sample of all the different types of plates that you will run across.  What other types of plates have you seen?