From LQWiki

I think this should be merged with latency and Lag (more a slang term) should point to latencty. - Ror

yea, but the term "lag" more often is used to discrabe any slowdown or chopy gameplay, or slow connection .. latency is just how long it take for packets to get from 1 point to another ... so they are a bit diferent, as why i didnet just add it to latency from the start - SciYro