Hello,
Precum is a clear lubricating fluid that is released from a man's penis when he is aroused and this is basically released from the Cowper's glands.
Pre-ejaculate does not usually contain sperm unless there has been a previous ejaculation even 24 hours prior. Basically preum itself does not contain sperms but it may pick up the sperms which have been retained in the penis after a previous ejaculation. Although urination removes most of the sperms left behind after ejaculation but it does not remove all such sperms. Some may remain viable for upto 5 days under ideal circumstances in the body and then may get mixed up with precum.
Hope it answers your query. Wishing you good health. Take care and regards.