The Hero Panel, which can be displayed by pressing H, holds a summary of a characters statistics, experience, faction, and titles:
The top of the Hero Window shows a picture of your character, along with their name and class of your character.
Level: displays your character's current level. Mousing over this will show a summary of what level does.
Skill Points: shows the amount of Skill Points your character has gained. Mousing over this will display the amount of skill points you have used over the amount you have gained.
The green bar shows the relative amount of Experience your character has gained out of the needed amount for reaching the next level. Over it, in white, there is the total number of Experience points your character has gained. Mousing over this will tell you how much Experience your character needs to reach his next level or skill point.
The account's Factions tab shows the amount of Faction you have gained through PvP battles or quests. There will be several bars indicating types of faction you have earned. Mousing over each bar will give you a short description of the Faction, and the amount of faction you have spent over the overall amount earned.
The Character's Titles tab tracks the progress of the character's titles.