What levels mean

Level
0: Normal Men
1-3: 'Low Level' - most competent NPCs are in this range.
4-6: 'Mid Level' - experienced, capable characters.
7-8: 'High Level' - renowned adventurers and suchlike.
9-14: 'Name' or 'Lord' level; these characters can found their own dominions.
15+: Legends; these characters are extremely rare.

Specific Levels
8th Level - a renowned figure in the community, such as a Halfling Shire-Reeve (max level).
10th Level - a Lord, such as an Elf Lord (max level).
12th Level - a Great Lord, such as a Dwarf Lord (max level).
14th Level - maximum level for Human Lords.
15th Level - a legendary figure or Saint of Law or Chaos.
20th Level - The greatest human heroes of yore, such as Val Trionos, able to smack down Sauroth with the aid of your buddies. Able to contend with the Lords of Law or Chaos.
36th Level - maximum level.

Stables of Characters
At higher level it is wise to maintain a stable of PCs and Retainers, with a mix of robust but limited demi-humans alongside more fragile yet potentially unlimited human characters. Demi-humans often make good initial PCs, but will eventually be overshadowed by their human comrades.