Pepper actually refers to several different kinds of plants. Black or white pepper (genus Piper) is a common food spice.
There are different kinds of pepper. When people talk about "salt and pepper", they're usually referring to black pepper. There are also a range of peppers that have different levels of "spiciness" or hot sensation: bell, chilli, banana, bell, cayenne and more. It also has the interesting property that some pests may not like it. Allspice is in the pepper family.
The "heat" or spiciness of peppers are measured on a Scoville scale or in Scoville heat units (SHU). It measures the amount of capsaicinoid in the peppers. Higher numbers mean hotter. A banana pepper measures at about 500 SHU, while a Habanero pepper can range up to 570,000. (Law enforcement grade pepper spray is about 5 million SHU.)
Pepper is primarily used for taste, but may also have some health benefits. Black pepper assists in digestion, provides manganese, vitamin K and iron. Bell peppers are high in vitamin C, A, B6 and various carotenoids. They are a good source of antioxidants. Bell peppers may have a higher level of residual pesticides on them than many other vegetables
- Wikipedia's article on pepper
- pepper on the recipes wikia
- Visual guide to peppers on Miss Vickie's Pressure Cooker Recipes, also has a short description of a variety of peppers
- Wikipedia's article on Scoville scale