Go Rankings are, by name, an address stating how skilled someone is in the game of Go. These names are usually how one is known among Go Players.
Dan and KyuEdit
Among rankings, there are two kinds. Dan, and kyu.
Dan is a higher level in playing in Go than kyu, and if one is considered dan level, he/she is usually considered advanced. Dan rankings go through 1 dan all the way to 9 dan. 1p-7p, where is considered a special title, is usually addressed as an advanced player, while 1d-9d, where 9d is considered special title, are considered Professional players.
Kyu is a lower level of playing in Go than dan, and if one is considered kyu, he/she is considere average or beginner. Kyu levels start from 1 kyu, and go down infinitely, though usually most aren't considered less than 30k. The larger the number, the worse you are. 30-20k are considered beginners, 20k-10k are considered Casual Players, and 10k-1k are considered Amateur Players.