Fresh (for food) is newly made or obtained, i.e. not frozen, processed or pre-cooked. Fresh food is often thought to be the healthiest kind of food, because it conserves its vitamins and does not have added salt or sugar.
When applied to water, it can also mean not salty, i.e. water in lakes and rivers rather than the sea or ocean. The largest body of fresh water in the world is Lake Superior, one of the Great Lakes on the border between the United States and Canada.