Peas are cooked as a vegetable in many cultures.
Types of pea 
The immature pea is called the garden pea. It is sold fresh (usually in the pod), tinned, or frozen.
The mature pea, which dries naturally in the field, is known as the marrowfat pea. This name is recorded by the OED as early as 1733. It is grown mainly in Britain, but many are exported to the Far East. One of the oldest export varieties, popular in Japan for the last hundred years, is called Maro. This has led some people to assume mistakenly that the English name marrowfat is derived from Japanese. In Japan and other Far Eastern countries, such as Thailand, Taiwan and Malaysia, the peas are roasted and salted, and eaten as snacks. In the UK, marrowfat peas are used to make pease pudding, a traditional dish.
Ways of eating peas 
Dried peas are often made into a soup or simply eaten on their own. Fresh peas are often eaten boiled and flavored with butter as a side dish vegetable. Fresh peas are also used in pot pies, salads and casseroles. Pod peas (particularly sweet varieties called mangetout and sugar peas) are used in stir fried dishes.
In the UK, dried, rehydrated and mashed marrowfat peas, sold as "processed peas" but usually known by the public as "mushy peas", are popular, originally in the north of England but now ubiquitously, and especially as an accompaniment to fish and chips or meat pies, particularly in "chippies" or fish and chip shops. Sodium bicarbonate is sometimes added to soften the peas.