The new metric was initially released in April, 2012 as '???' during a testing phase, being finally renamed to "pp" (Performance Points) on the 17th April 2012. In July 24, the (20120722-24) osu! release replaced the Ranked score system with Performance Points for every 30 minutes. At August 16, the pp system is now updated real-time.
The changelog can be found here
The performance points ranking can be found here 
It can also be found from the bar at the top (Rankings -> Performance)
The calculation formulaes involved are currently not publicly known, but some guidelines have been released:
- Favours skill, and cannot be truly farmed (though setting lots of great records helps).
- Weighs difficult maps higher, using a unique formula based on publicly unavailable statistics.
- Diminishes naturally over time (if you are inactive for a year you'll lose up to half your score).
- There are no penalties for "bad" scores — only rewards for good ones.
- All ranked and approved maps are included in calculation.
- Accuracy is considered.
- Play mod weightings are slightly adjusted for fairness.
- Updated in real-time.
- If your score is not in the top 600 scores for a map, you may gain fewer pp or not have that score counted.
Increasing your rank
Your performance rank is predominantly based on your performance on individual maps. The easiest way to improve it is to improve your rank on difficult songs. Do note that game modes are counted separately [which means, playing (osu!/Taiko/CtB) raises (osu!/Taiko/CtB) pp].
- Play better, rank higher on songs.
- Work on getting some really high ranks, not thousands of "okay" ranks.
- Get higher accuracy (even 1% difference can help light-years!)
- Rank on highly contested maps.
- Rank on harder difficulties.
- Improve old records.
- Get "SS" grade instead of just Full Combo/Perfect.
|Picture example. pp can be found at your account page under "General" tab.|