Your grammar sucks is a YouTube show hosted by the Nepal loving, Pitbull loving, Forehead extremist JacksFilms. It is a common inside joke that though it is marketed as been held every Friday, but like most things in John's career it can take weeks if not months for a new episode/installment. It can also be used to state someone's grammar sucks hence the name
Person one: Hey john where is the hatthe children are being burnt to crisp!
John: YGS LMAO (says this while low dabbing)
Person One: Yasss
Abbrevation for either:
-Your Grammar sucks! An internet show hosted by Jack Douglass known on YouTube for "JacksFilms"
-You got surved, this sentence is usually said after getting burned, metaphorically speaking.