How to use a laptop with cd decks and a mixer for DJ'ing?

right im a dj i curently use vinyl and want cd decks. ive seen someone connect cd decks and their mixer up to laptop and on the laptop they had what looks like a program that you can use to stream the tracks to a cd deck. what kind of program was this? and how do you connect cd decks and the mixer up to a laptop. is it only specific brands used for it like Pioneer





Im pretty sure the setup was: a macbook, Pioneer djm 800 and P cdj 1000's.How to use a laptop with cd decks and a mixer for DJ'ing?
I don't know.