An indie game, short for independent video game generally refers to a video game made by a single developer or small team without the support from a large video game company. Some indie games have become very successful like Minecraft.
Indie game has no true definition, but has certain features, they are often made by one person or a small team, often smaller than mainstream titles, often not getting money from a publisher. But being without a publisher means that they have no-one telling them what they can and can't do, giving them much more freedom to make a game they want to make. But making a Indie game does not mean they have no publisher. Indie game developers often go to crowd-funding sites to help fund the game, but often make very little profit.
Indie games started on PCs where it currently remains. Indie games become popular as shareware. But as better technologies came out people began to expect more from these small teams, indie games have seen a huge rise in the later half of the 2000s.