A character level is a character's total level. For a character with levels in only one class, class level and character level are the same thing.
Example: A character who is a wizard 4 / fighter 3 / rogue 2 has a character level of 4 + 3 + 2 = 9.
Max Character Level in NWN2
No Expansions: Level 20
With Expansions: Level 30
See Neverwinter Nights 2 Complete at http://gog.com