tldr

Community-maintained cheat sheets for command-line tools, showing the five things people actually run instead of the forty flags a man page documents. Type the command name, get worked examples. It solves a specific, daily frustration: man pages are reference material written for people who already know the tool, and most of the time you just want the tar invocation that extracts a gzip archive. Thousands of contributors, translated into dozens of languages. The tradeoff is depth — it is deliberately shallow, so anything unusual sends you back to the real documentation. Treat it as the first lookup, not the only one.