Disambiguation is a concept that got little public attention before Wikipedia (like the @ symbol was little-used before email). When a Wikipedia article needs a title, but another topic already is using that name, what do you do? By devising a method to reduce the ambiguity.

What Wikipedia usually does is adds parentheses after the formal title, selecting a phrase that most closely describes what is unique about each one. For example, several dozen John Smiths have met Wikipedia's notability requirement, so there are no less than six cricketers and seven footballers disambiguated only by their birth date.

And all relevant examples (including similar spellings) are collected on a single page, the disambiguation page. One of my favorite ironies of Wikipedia: disambiguation has its own disambiguation page, naturally found at Disambiguation (disambiguation).