Meaning:
Lit. “a hit, strike” – in German. This is a loanword into Polish and since 19. century has been used to denote a successful action in card games or billiards. As well as having sex. Mostly among thieves and criminals, not in any official communication.
Then, after 2010, the “sztos” got extremely popular among teenagers as a tag for something impressive, amazing. You say “to jest sztos” then – if the party was good, you enjoyed a movie or got the best note at school. You always use it as a noun – an adjective based on “sztos” does not exist.
Obviously, the word then got picked up by marketing and the media and now it is used by people well into their 40s.
Examples:
Konwencja KO to był sztos! I gdybym nie była wyborczynią Trzaskowskiego, byłabym jego fanką.
To ciasto to prawdziwy sztos! Bardzo nam smakowało, każdy się zachwycał więc polecam dalej! Przepis w komentarzu.
Pojeździj po świecie, stwierdzisz, że Polska to jest sztos sztosów.