Dota game modes and some relevant commands

Dota has several different game modes. Before you enter a game lobby the title should tell you what mode you are going to be playing. The four main ones that are used in public games are: -AP (all pick), -AR (all random) -RD (random draft) and -SD (single draft).
With -AP everyone can choose from any of the 100+ heroes. If someone doesn't want to choose a specific one they can type "-random" and the game will assign them a random hero.
-AR is exactly what the name says. All 10 players receive a random hero.
In -RD the game chooses (drafts) about 20 random heroes for everyone to pick from. Then, the two team alternate picking heroes in the order 1-2-2-2-2-1.
With -SD, each player is assigned three random heroes to choose from. These heroes will include one of each of the three skill types: strength, agility, and intelligence.

RD (random draft) mode

There are two main ways to play Dota matches and that is -EM and non-EM. -EM stands for easy mode and all players will gain more gold periodically and gain more experience from creeps than in non-EM games. Also, towers are weaker and easier to destroy in easy mode. The -EM if it is going to be active in your game will be displayed in the title right behind the game type, for example: -APEM (all pick, easy mode). I recommend you play -EM games if you are new to Dota because in non-EM games you can get behind very easily and it's hard to catch up with gold income being low.

A few other game modes that aren't as common in public games, but are still around, are -DM, -CM, and -CD.
-DM is added to other game modes, for example: -APEMDM (all pick, easy mode, death match). -DM means that when a player's hero dies he will get to choose another hero, keeping the items he had and the amount of levels already earned.
-CM and -CD are pretty similar. They mean Captains Mode and Captains Draft. In both of them, blue and pink (team captains), take turns banning heroes and then choosing the heroes they want on their team. Once both players have finished, the players of that team choose the hero they want to play. In -CM all 100+ heroes are available. In -CD it's a draft and captains choose from a group of 20+ heroes. These two modes are pretty rare in public games but are very common in tournament games and between two organized teams.

After heroes have been picked or assigned it is possible to swap with teammates at the start of a game, as long as the timer hasn't reached 0 and started counting up. All you do is type "-swap #", the number being the player on your team you want to switch with.

Also, if you don't like the hero you've been assigned you can type "-repick" (again, as long as there is time). In -AP this allows you to go back and pick someone in case you did -random or if you're playing -AR it will assign you another random hero. You can only do this once per game and remember that if you do repick your hero you will lose a chunk of gold from your starting amount.

Drow Ranger