The "Puberty FAQ and Information - THIS MIGHT ANSWER YOUR QUESTION!" announcement (colored in green) answers this (I wrote it)
Precum â€“ this is a natural lubricant produced by Cowperâ€™s glands and comes out of the penis when a guyâ€™s horny, usually during or before masturbation. It acts as a natural lube and cleans out the urethra (the penis hole)
Precum isn't the same as clear cum. Precum is NOT underdeveloped cum - so if you ejaculate and it's not white, it's not precum. Precum comes out when you're horny or during masturbation - not at climax!
This is a very common question. I try to include all frequent questions asked in the Puberty FAQ & Information announcement. Before someone makes a thread, they should look at that announcement first. I worked pretty hard on it!