Coriander is well-known as a staple spice of Indian Cookery, and is present in almost all curries. In the UK, coriander powder is the most popular form, but there is an increasing trend towards using the whole coriander seed form, because that is the more authentic method used in India (where the spices are typically crushed just before use). We also provide the leaves, for lighter curries.
Coriander seeds are usually ground up (e.g. with a mortar and pestle) and then the resulting powder is used as coriander powder (above). Freshly-ground coriander powder (i.e. from seeds) does have a more intense flavour than already-ground powder.
Coriander leaves are often used in the lighter curries. They have the same coriander taste as the powder or seeds, but do not have the same bitterness which is often desired in stronger curries. Nonetheless, they work well in all curries, and are a great all-purpose coriander.