From Liquipedia Warcraft Wiki
In this Portal you can find all the information you need about Warcraft III Tournaments.
Team Tournaments (2 player teams excluded)
have not precise features. A group of players can represent a country, a team
or a race. It can aslo be an ad-hoc team. There is usually between three and ten player in a team, matches can be 1v1, 2v2 in different format. Here you can find 3v3 and 4v4 tournaments too.
Tier 3 team tournaments
Tier 3 tournaments offer a smaller prize pool and less prestige than Tier 2 tournaments but still draw a high level of competition.
Monthly individual tournaments
Monthly Tournaments are tournaments that occur regularly and most often as monthly events. They are generally the culmination of a Weekly Tournament series.