Further means to a greater extent or degree, or at a greater distance. When you walk further down the street, you're going more distance in that direction. When you dig further into a problem, you're investigating it more deeply. If a teacher says, “Let's discuss this further,” they want to talk about it more.

The word also means to help something advance or progress. A scientist might do research to further our understanding of the ocean. A mentor furthers a student's education by teaching them new skills. When you further a cause you believe in, you're actively working to help it succeed.

People often confuse further with farther, but there's a useful distinction: use farther for physical distance (“The library is farther than the park”) and further for figurative distance or degree (“We need further discussion”). However, many people use further for both meanings, and that's widely accepted.

The phrase “furthermore” means “in addition” or “moreover.” If you're making an argument, you might say, “The plan is too expensive. Furthermore, it won't work.” You're adding another reason to support your point.