Depending on the Go-server, amateur ranks start at 20-30 kyu. 20-kyu (or 20k) is supposed to need one handicap stone less than 21-kyu, 21-kyu one handicap stone less than 22-kyu, etc. Countdown goes down to 1k.
After 1-kyu follows 1-dan (or 1d). The Dan-ranks also are one handicap stone apart. Again, depending on the Go-server, the highest amateur dan is somewhere between 7d and 10d (most have 9d as highest rank, just like the professionals, with 10d as special title won in a tournament).
Rating for professionals, which is not determined by the Go-server. To distinguish them from amateur dans, their dan-rank is followed by a 'p' instead of a 'd'. They are outside the Go-server rating system. Professional ranks are only about half a handicap stone apart.
Individual player ranks
Depending on the Go-server, ranks of a player can vary quite a lot. The same player can be a 12k on one server, an 8k on the next, and a 14k on another. This is because of the different player pools and an inflation tendency caused by the mathematical model to calculate ranks (look up Eloi rating system in Wikipedia).
Unrated / unranked players
If a player either hasn't played enough games (mostly 4 or less) or has shown a great disparity of strength (winning against 2k but losing against 10k), most Go-servers will display the player as unranked with a suggestion of the rank (e. g. 5k?). This rank is only a suggestion, but the probability of it being right isn't very high. Most experienced net-players don't really like playing against unranked players because most of the time, they turn out to be absolute newbies who don't know what they are doing.
Go in general:
The seven greatest Japanese Professional Go titles with the prize money:
With the new rules established in 2004, winning Kisei, Meijin, or Hon'inbou automatically elevates a pro to 9-dan, no matter their former rank. Winning Juudan, Ouza, Tengen, or Gosei gives them 8-dan, and if they manage to defend the title the next year, they become 9-dan.
If a pro has won a title, said title is added to their name as suffix. If they hold several titles, only the highest is added.
Byou-yomi – time a player has to make a move after the original thinking time has run out
Handicap stone – stones black is allowed to place at the beginning of the game. Used to have players of different strength play on equal ground. One stone is the equivalent of about 10 moku
goban – Go board
goke – bowls where Go stones are kept
Ko-fight – situation of capture and re-capture that could go on endlessly. Go rules say that a player can't immediately recapture but has to wait a turn
Ko-threat – situation where the opponent has to react in fear of losing a lot of territory. Used in Ko-fights to keep the opponent from capitalizing on a captured stone until one is allowed once again to recapture.
Komi – points White gets to make up for Black moving first. Nowadays 6.5 moku.
Moku – territory points. They are the empty spaces completely surrounded by a player's color
shidou go – teaching games. The teacher doesn't play to crush, but to point out mistakes and challenge the student
tsumego – life or death problems, used to practice reading a situation very quickly