Folded cards

What does the dealer do with folded cards in a cash game or a tournament?

i think he puts the folded cards aside, along the cards between the flop & turn and turn & river

I also think that the folded cards are inserted to the side, and then all the cards are distributed on a new basis.

I think they put them aside, they are so-called burnt cards ...

A burn card is the top card taken from the the deck and before the flop, turn and river are dealt.

I'm my experience, the dealer will gather them up and put them in the "muck" (the pile of cards kept face-down, usually under or near the pot). The burn cards (the cards taken from the top of the deck before the flop, turn, and river) are usually kept nearby but separate as a confirmation they have been burned