Like crunch said.. and it's based on your score... usually means you are in the top 100,000 players... (based on the install base of about 10,000,000). If you play the same game mode frequently enough then you should find yourself hitting the top 1% fairly easily
Its on your elite page, scroll down a bit you will see 2 white bars labled core and hardcore, click to expand which one you play and it will show the game modes you played.
