The Free Folk do not kneel for anyone, while the kneelers are subject to laws, lords and kings. The Free Folk view the kneelers as lacking freedom, whereas the people of the Seven Kingdoms view the "wildlings" as savage, lawless and uncivilized killers, rapists and thieves. However, surviving Free Folk have knelt forcefully to Stannis Baratheon and willingly for Jon Snow.
In the books
In the A Song of Ice and Fire novels, "kneelers" is also a derogatory term used by the Free Folk to refer to those south of the Wall, as they view kneeling as an act of renouncing one's freedom.