What do you mean with lag?

I just wanted to ask, since the trend seems to be, that todays players tend to mix lag with bad FPS.

Lag is usually caused by network problems or server structure problems. Bad FPS is bad FPS cause by low end machine or too high video settings. Also numer of addons may cause this.

At least this is how it is in simplified terms.

Just wanted to talk about this, since it is very important to tell the difference between these two when reporting issues and complaining about performance issues.