What does ROFL mean while texting?

ROFL:Roll on floor laughing.

Lol: Laugh out loud.

Lmao: Laugh my a** off

Gtg or G2g:Got to go

Brb:Be right back

Idc:I don't care

idgaf: I don't give a f***

Idk:I don't know

Hbu: How about u.