The difference between pottery, china, porcelain, ceramic, etc. may seem obvious to many, but to someone new to collecting, and now even newer to selling, I needed to know. Now that I do I would love to share it with you.
The most general of the terms "ceramic" applies to minerals dug from the earth, mixed in various formulas with water and sometimes organic materials, shaped, decorated, usually glazed, and heated to a durable hardness. The different terms within the catagory such as "pottery", "porcelain", "earthenware", "bone china", etc. all represent the standard formulas, and have come to popularly represent quality grades.
Here are a few that I have found most common. It is by no means an exhaustive list. I invite my fellow sellers to add the ones they are aware of, and correct me if they feel I am in error. In my store Abigail's Displays, I take care of errors with a money back guarantee. I may not have the biggest selection, but I make my customers happy. So here, beginning with what is generally considered the most common are some terms you may want to know.
Pottery is, like ceramic, a very generic term. It is generally used to refer to items made from common clays. It is often but not exclusively handmade by the artisan, or craftsperson using their hands, molds, or a potter's wheel. It is generally fired at lower temperatures, sometimes as low as 800 degrees.
Earthenware, is the term used by archiologists when discussing pottery with historical significance.
Terra cotta is type of pottery usually made without a glaze and of a specific color at a lower temperature.
Stoneware is a dinnerware which is commonly called "everyday" dishes.
China, in this context, originally refered to a ceramic dinnerware coming out of the country of China which was particularly fine and exceptionally white. It was a standard of quality unknown elsewhere at the time. The mineral Kaolin was used to achieve this look. Many of the different European formulas developed in an attempt to match it. This watered down the term, which now refers to any high quality, natural material (as opposed to man made) ceramic, dinnerware or otherwise.
Bone china, which is a common term, but not seen that often actually contains ground bone.
Porcelain is the term currently being used to refer to the highest quality ceramics. Kaolin is used in the manufacture, and it is usually very delicate. Another member reminded me that "the most significant identifying factor for porcelain is it's translucence. You can see a shadow of your finger through it if you hold it up to the light. If porcelain is very heavy, the shadow will be very faint, but it should be visible. All other ceramics are opaque and do not transmit light." (Thanks Carol)
I don't know if this helps you, but it took me a while to come to the understanding that these terms have only subtle differences, and truly aren't very important. The bottom line is, as with any collecting, buy what you like. When you have seen a lot of examples of the different types. You will know quality because it stands on its own. And when you are looking for replacement pieces of your favorite china, I hope you will start with Abigail's Displays.