The toplaners are usually tanks, fighters and sometimes shooters who doesn't need a support, their job is destroy the maxims turrets.

The junglers are usually tanks, fighters and assassins. They don't have a line, their job is help the lines killing the enemy by sneaking in to make it easily, this is called a gank. The jungle have monsters that the jungler can kill and give him gold too.

The midlaners are assassins and wizards, their job is help the jungler giving him vision of the other jungler and help the other lines, cause he can help and rotate so easily.

 The botlane, formed by the ADcarries and the support. The ADcarries should be the greatest source of damage, attacking from a distance and be protected for him team, this is so important because it is very weak and the enemy team can kill him easily. The main job for the support is protect the ADcarries and give vision to the team, and it is the most underrated role. The supports can be tanks, utility support (they use shields and cures) and wizzards supports (who in my opininon aren't good supports).