Textured Vegetable Protein, or TVP, is pretty much exactly what it sounds like. It's generally sold dried in little unattractive beige nuggets, which need to be cooked in a bit of liquid to be reconstituted. Like tofu, it is tasteless unless cooked in something flavourful. Unappetizing name aside, TVP is a brilliant invention for vegetarians - it feels and satisfies like ground beef.
TVP can be added to any dish you would normally add ground beef to. Great in chili. The texture is so much like meat (albeit chewy meat) that you can even fool meat eaters if you take the precautionary step of marinating the TVP in tomato juice for a while before cooking to hide the white colour. If you need TVP for a recipe but don't have any, you can make a reasonable facsimile by crumbling tofu (not too small) and freezing it, and then defrosting it. The tofu will pick up an interesting texture that is similar to TVP, if not as convincing.