Agatheron's Points of Light
Metagame > Tiers of Play
4th edition D&D is arranged into three broad-level groupings that tend have specific dynamics of their own. “Heroic Tier” covers characters who range from 1st to 10th level. They are still set apart from the general population in that they are pioneers and leaders, who have taken the risk to pursue a life that goes beyond their humble beginnings. They also begin to make a difference in the world around them, albeit on a small scale, assisting a local town, making the world a safer place.
They are heroes after all.
In game terms, this is also where characters begin to develop a sense of self. The people playing the characters are also getting a sense as to how their own characters play, and get used to their newfound abilities.