Blocky, sweet cultivars of Capsicum annuum.
Bell peppers are probably the most common group of cultivars of Capsicum annuum, and definitely the most common sweet (ie. lacking in capsaicin) variety. As well as lacking the 'heat' of most other chili peppers, bell peppers are a blocky shape and have a relatively thick wall.
Bell peppers are typically green when unripe and then ripen to a red color. Green unripe peppers are commonly eaten but they are not as sweet as the red ripe fruits. A wide range of cultivars have been produced, resulting in a wide variety of colors (including yellow, orange, purple, 'chocolate', black, white), sizes, and climate preferences.
Popular varieties for garden use include California Wonder (Tobacco Mosaic Virus resistant), and Gypsy (relatively small, yellow, but hot weather tolerant).
Use this tag for questions specific to bell peppers. Use the peppers tag for more general pepper growing questions.