Tom yum or tom yam is a Lao and Thai, clear, spicy and sour soup. Tom yum is widely served in many countries such as Cambodia, Brunei, Malaysia and Singapore, and has been served around the world.
The words "tom yum" are from two Tai words: "tom" and "yam". "Tom" refers to boiling process, while "yam" refers to a kind of Lao and Thai spicy and sour salad. Thus, "tom yum" is a Lao and Thai hot and sour soup. Indeed, tom yum is famous for its distinct hot and sour flavours, with fragrant spices and herbs put together. The basic soup is made of stock and fresh ingredients: lemongrass, kaffir lime leaves, galangal, lime juice, fish sauce, and crushed chili peppers.
In neighbouring countries like Malaysia and Singapore, the name tom yum is used widely for various spicy soups which are different from true Lao and Thai tom yum. So, people are often confused by the difference.
Tom yum paste is made by crushing all the herb ingredients and stir frying in oil. Seasoning and other preservative ingredients are added. The paste is bottled or packaged and sold around the world. Tom yum made with this paste may have different characteristics from that made with fresh herb ingredients. The soup often includes meats such as chicken, beef, pork, or shrimp.