Bay leaves are a form of laurel leaf, and are grown and used all over the world. They have a mild herby flavour that is not specific to any one style of cooking. For example, they are commonly used in mediterranean cooking, as well as in Indian cooking.
Uses of bay leaves are diverse, including soups, curries, stews and stir-fries. They are often a component of garam masala.
Bay leaves add a fragrance to any meal: just pop one in the pot or pan. If you add them whole, you can usually pick them out at the end just before serving.
Bay leaves are mildly antimicrobial, and once long ago were valued as a cure for a number of ills such as indigestion, though it's not nearly as powerful as most other spices. Nonetheless, bay leaves do still have some uses, and have been shown to help the body to regulate blood sugar levels. Some people take bay leaves with boiling water, as a form of herbal tea.