Documentation is the written instructions, records, or explanations that help people understand how something works, why decisions were made, or what happened. When programmers write documentation for their software, they're creating guides that explain what each part does and how to use it. When scientists keep careful documentation of their experiments, they're recording every step so others can repeat the work or understand what they discovered.

Good documentation answers questions before people have to ask them. If you buy a new board game, the documentation (the instruction booklet) tells you the rules, the objective, and how to set up the game. When your teacher asks you to show your work on a math problem, that's a form of documentation: you're recording the steps you took to reach your answer.

The word can also mean the act of creating these records. A historian documenting what happened during a major event is gathering evidence, taking notes, and organizing information so future people can understand it accurately. Documentation turns knowledge and experience into something permanent that others can learn from, even years later.

Without documentation, people would have to figure everything out from scratch or rely on memory, which isn't always reliable. Well-written documentation saves time, prevents mistakes, and preserves important information.