When excited, what is the fluid that comes out of the penis?

Prostatic fluid

is a colorless, transparent mucus-like substance secreted by the male prostate gland. Its main components are water, glucose, zinc, calcium, etc., containing a small amount of white blood cells, acid phosphatase and other components. Prostatic fluid will be released when male sexual excitement, which can play a role in lubricating and reducing penis friction. It can also help protect sperm and increase its viability.

It should be noted that if the color, smell and texture of the liquid flowing out of the penis are obviously abnormal, it should be treated promptly.