N.F.T.s stands for Not For Trades. Sticker collecters use this word to show that a particular sticker is not for trading (exchanging stickers). Sticker collecters trade stickers when they want something particular from another. Trading is based on quantity, quality, size and fairness. Some sticker collecters have a N.F.T.s page which is a page full of stickers that are not for trading.
"That sticker is a N.F.T.s because I like it a lot"