Lag is latency, has nothing to do with video or CPU. .
In today's world, lag has gone from having a specific meaning (latency in multiplayer gaming which can cause rubber banding and missing shots that should have hit) to becoming a more general use word with broader meaning.
Most people who say "lag" now mean low FPS.
This change of the meaning seems to have come from console gamers who want to be cool like us PC gamers, but they incorrectly used one of our words. Pretty lame and totally not cool. I'd arrest all those console gamers but there isn't enough prisons to store them all, and sadly it isn't legal to just execute them all, being an internet cop is hard sometimes, and the pay sucks.
In 7 days to die, frustratingly enough, lag takes on a 3rd meaning.
It could also mean what some like myself are experiencing, where even in single player, even with graphics turned down, the game quarter second freezes up completely then goes back to normal.
Soo to summarize here is how this should go.
LAG: latency in multiplayer, causing rubber banding or temporary lost input.
LOW FPS: Low frames per second, caused by poorly optimized game, or just not having enough horsepower on your cpu\gpu.
Short freeze: short duration freeze, the game might still be running just failing to show any frames during this freeze (like in 7d2d)
freeze: the game froze up and you had to restart the game\computer.
crash to desktop (C2D): like a freeze only it put you right to desktop, no need to do control alt delete or alt f4, or hit reset.
crash to couch: What happens after a long hard day at work.
sugar crash: What happens after eating or drinking sugary foods!
crash to crash: What happens after driving while intoxicated.
social suicide: You decided to start playing video games. You might talk to people online, but it isn't the same thing, your social life is over.
WORDS WORDS WOOOOOORDS!!!!
But we are in the idiocy generation, so all hope of getting consistent use of words is lost. Heck, I to make constant conversation and grammar mistakes. We are all idiots. Anyone who thinks himself not a fool is a greater fool indeed. Good luck humans, you suck.
NOW LET ME TURN YOU ALL INTO ZOMBIES RAAAAAAAAWR!!!!