What’s is low disk space in iPhone 11?

What’s is low disk space? I can’t send pictures and every picture has an exclamation point or is blurry. I’ve done the settings change and other tweaks- is family sharing part of this problem? Please help. I only have 1200

pictures and 50 videos. Not a big gamer either. Not much else on my personal phone. Thanks.

[Re-Titled by Moderator]