The Elo points system used in Ludopoli is for internal (i.e. on Ludopoli rankings) use only; it doesn't have any value in official chess rankings.
What is the Elo points system
The Elo points system is used to numerically define the skill of a chess player. The name comes from the American engineer and famous chess player Arpad Emrick Elo (born in Hungary). He developed this system at the request of the USA Chess Federation (USCF, founded un 1939).
The Elo system doesn't simply record the wins or losses of a player, but gives (or takes) points based on the difference in skill between the players, using a gaussian distribution of probabilities. In other words, by winning a match against an opponent (whose Elo points are higher), you'll win more Elo points than those gained by winning an opponent with fewer Elo points. When losing, you'll lose an amount of Elo points proportional to the difference in Elo points. Using this system, a draw is considered as a halfwin/halfloss. The Elo points are updated after every match.
The Elo points System was officially adopted by the USCF in 1960, being judged as the most fair and accurate system to measure a player's skill in chess. In 1970 the system was adopted by the FIDE, and other chess federations worldwide. Later the federations have learnt that the "weaker" chess players have a higher chance of winning than the one predicted by Elo, so have modified the system accordingly. They mantained, however, the name "Elo" as a tribute to the founder of the system.
The Elo points System in Ludopoli
ELo's ideas were adopted by all the chess federations, albeit every federation uses a variation of the ortiginal system. That's why, when speaking of Elo points, we should refer to them as FIDEElo points, ItaliaElo points, USCFElo points and so on.
In Ludopoli, the official Elo point System of the Italian Federation is used (commonly referred to as ItaliaElo points System).
Every new player will start with 1000 Elo points.

Using the difference between two opponent's Elo points, you can find in the ELo points table below the expected winning percentage of both players. If the difference in Elo points is bigger than 350 points, the two players cannot play a match, as it would be unfair;

To know the Elo points gained (or lost), you compare the actual Elo points gained after the match (P) (1 for a win, 0 for a loss, 0.5 for a draw) with the expected result (PA); the Elo points of a player are updated after every match by using the following formula:
NewElo=OldElo+K*(PPA), with K=20.
Ex. 1: player(1) Elo pts. 1352, player(2) Elo pts. 1227, difference +125(% 67/33). Player(1) wins. The Elo points are updated as follows:
Elo pts. player(1) = 1352 + K(20) * (1 – 0.67) = 1359;
Elo pts. player(2) = 1227 + k(20) * (0 – 0,33) = 1220.
Ex. 2: player(1) Elo pts. 1352, player(2) Elo pts. 1227, differenza +125(% 67/33). Player(2) wins. The Elo points are updated as follows:
Elo pts. player(1) = 1352 + K(20) * (0,5 – 0.67) = 1349
Elo pts. player(2) = 1227 + k(20) * (0,5 – 0,33) = 1230). 