These graphs show the item levels of active characters at max level. By active, we mean characters that killed something (creature / player) in the past four weeks.
The first chart shows the distribution of item levels, i.e. the percentage of active characters for each level. When current pvp season comes to it's end, you easily can figure out the item level of latest pvp gear.
The second and third chart display item level rising over time since April 2014. It features the top 1%, 2%, 5%, 10% and 25% of players as well as the average iLvl.