These days most (non-native) people learning to read and write Chinese characters (or "hanzi") will use SRS apps, mnemonics and drills. These are great but they can leave you open to being tricked by similar-looking characters.
This site tries to help with this by collecting similar-looking characters that often get confused with each other and presents them in a way that highlights their differences.
Olle Linge's Hacking Chinese article: Horizontal vocabulary learning inspired this site. I'd encourage you to also read the post You can’t learn Chinese characters by rote, as the horizontal learning provided by this site is only one small part of the diligent hanzi learner's toolchain. More recently, Horizontal Hanzi was mentioned in Olle's article Panning: Keeping similar Chinese characters and words separate, along with other great resources worth checking out.