Key resellers are sites that sell game keys at (usually) much lower prices than traditional retailers. They do this through a combination of ways, like selling keys that come in a bundle, that were on a sale and many other ways.
The reason why we separated them from traditional retailers is that these stores have been the subject of a divisive discussion for a long time.
The reason we include them is that you can buy keys on these sites usually for very big discounts, sometimes quite ridiculously cheap. In 99 % of cases, they will work the same as a much more expensive key would. For many people, especially people from countries with lower standards of living, this can mean big savings that have a significant impact on their life, while also playing the game and not resorting to piracy.
If you are buying on these stores, we have a few recommendations to follow: