I've seen tempeh in my vegan cookbook and hear that it comes from the soy plant. How does it vary from tofu if so? Is it something I can make at home or would I probably have to buy it?
Tempeh is a fermented soybean product, which is typically bound into a cake-like form by a type of fungus (Rhizophus oligosprorus). To create tempeh the beans have to be incubated and steamed. Tempeh has a firm texture and an earthy/nutty flavor, which develops as it ages.
Key differences between tofu and tempeh:
Tofu is made by curdling fresh soy milk with a coagulant, while tempeh is a whole soybean product (giving it a higher protein and fiber count, albeit slightly higher calorie count as well). Tofu has hardly any taste, and is able to take on the flavor of whatever you're cooking it with, while tempeh has it's own slightly nutty/earty flavor that persists.
You can make tempeh at home, however you would need to buy the Rhizophus oligosprorus to add in yourself. Here is a quick and easy recipe for making tempeh at home: http://veganlovlie.com/how-to-make-tempeh-easy-method/