How powerful one is in a given class. This is on a single class basis. What I mean by that is if you had a character that was a lvl 4 ftr / lvl 5 rogue your ftr class level is only 4 and your rogue class level is only 5.
the relative level of a class within a class series that represents its hierarchical placement based on complexity and responsibility in relationship to the other classes within the series.