Sperm is a sticky liquid.
This liquid comes out of a man’s penis.
This happens during ejaculation.
This article tells you what ejaculation is:
https://refu-tips.de/en/my-friend-told-me-that-he-ejaculated-what-does-that-mean/
If you swallow sperm you cannot get pregnant.
But sperm can carry diseases.
Even when the sperm is swallowed.
If you are not sure if your boyfriend is healthy, it is better not to swallow his sperm.
Sperm tastes different to everyone.
Some people like the taste.
Some people find sperm disgusting.
Both are ok.
You do not have to swallow sperm.
And nobody should force you to swallow sperm.
Not even your boyfriend.