Kimchi is simply put: Korean pickled vegetables. Often made of Chinese cabbage and/or rettich, inlaid in salt (water) and Korean pepper powder. It's meant to be kept for a long time and to survive the winter, but there are also summery varieties that don't keep as long. For the taste you can add extra ingredients like garlic, ginger or spring onion.
How to use ?
In Korea it is customary to serve a number of small side dishes (banchan) in addition to a main course. At least one of those side dishes will be kimchi, a meal without kimchi is actually unthinkable. Kimchi is also used to flavor other dishes, such as soups, stews, rice dishes, etc. Or used in pancakes, dumplings (mandu) and nowadays even rice cakes (tteok) and bread. The taste of kimchi is fresh acidic, not salty because of the fermentation. Furthermore, it depends on the variant whether it tastes fresh & light or slightly warmer & darker.