I heard Snowballing in a lot of league of legends gameplay videos and I don't know what it means. For example I hear Renekton can snowball really hard.
Having never played DOTA, LoL, or any other games of this genre, I am faced with the daunting task of picking between 50+ heroes to play. They each seem to have a role, such as Carry, Initiator, ...
What does backdoor technically mean in strategy games like DotA or League of Legends? Is it an accepted tactic or there are some rules that forbid it?