What is the difference between pre-cum and cum?

Pre-cum, also known as pre-ejaculate, is a clear fluid that may be released from the penis before ejaculation. It can contain sperm and help lubricate the urethra. Cum, or semen, is the white, milky fluid that contains sperm and is ejaculated during orgasm. The main difference is that pre-cum is released before ejaculation and cum is released during ejaculation.