The World Championships are annual competitions organized by the International Ice Hockey Federation (IIHF). This competition is played according to the IIHF rulebook and shall not be confused with the World Cup, which is a tournament hosted by the National Hockey League and played according to the NHL rulebook.
The World Championships are traditionally held around April-May every year. NHL players are allowed to participate, but since the tournament coincides with the beginning of the NHL playoffs, only the players playing elsewhere than the NHL and those who play for teams that have been eliminated from the playoffs can participate.
Modern World Championships are built according to the promotion and relegation system; therefore, these tournaments nowaday have four divisions and over 40 national teams participating.
The World Group is the main event of the World Championship. It showcases the 16 best nations worldwide, divided in 4 groups (A, B, C and D). A preliminary round first has all teams play against all other teams from its group. The three best teams of each group advance to the qualifying round.
For the qualifying round, two groups of six teams are formed - one with the teams from groups A and D, and one with these from B and C. The results from the preliminary round are kept, and the teams play against those that were not in their preliminary round group (for instance, group A teams play against group D teams). The top four teams of each of the two qualifying round groups will advance to the next step.
From this point, the tournament switches from a round-robin format to a knockout format. All eight qualified teams are pooled together, and the first team of each qualifying round group plays the last team of the other qualifying round group, while the second of each group faces the third of the other. The winners advance to the semi-finals; the winners of the two semi-finals matches face in an ultimate match crowning the World Champion, while the two losers meet up for the bronze medal game.
The teams that finished last in their preliminary round groups (A, B, C and D) meet up in the relegation round. Ultimately, the two grand losers of this round are relegated to division I.
Both divisions are separated into two groups of six teams; the winners of each of these groups are promoted to the next level above and are replaced by the two teams relegated from that level.
When there are more than 40 teams involved in the tournament, which is always the case nowadays, a division III is played. That division is played exactly as the Divisions I and II are, except that Division III competitions are played as a single group (unlike DI and DII) and that there is no relegation from DIII.