From HELP CLASS...
Code:
     Mercenary --  the basic warrior profession  
     Swashbuckler --  skilled in swift multi-handed strikes  
     Barbarian --  uncivilized warrior of brute force  
     Priest --  the basic clerical vocation  
     Paladin --  knight blessed by the gods of light  
     Hellion --  knight blessed by the gods of darkness  
     Shaman --  uncivilized cleric with spiritual powers  
     Rogue --  the basic adventuring profession  
     Scout --  skilled in woodlore and bush-fighting  
     Bard --  performer and minor magician
     Sorceror --  the basic wizard profession  
     Warlock --  worships and uses the elemental powers  
     Necromancer --  diabolical master of the undead  
From the above, you should get a fair idea of the IC nature of each class.  I'm not quite sure how much more you'd need to know to match your character concept up with the right class.  On MUDs with some of the more fancy class names (Auriger, or something??), then I can understand more information should be given because the name isn't very well known.