I've learned a new word just now,come'in

<<There was competitive drinking in the kitchen and foreplay in the darkened living room,where necking couples sprawled on the furniture and across the floor>>

First of all, I point out that there's holding a party in this context.

I've learned the word "necking" which means kissing, that is to say, if two people are necking, they are kissing each other in a sexual way.

Is that so? But the book which I'm reading is published in 1991.

Necking means kissing but making love means sexual intercourse.

Necking usually refers to passionate kissing.

since when do "making love" and "making out" mean the same thing?