A cheat sheet is a simple short document, typically 1-2 pages of notes designed to aid your memory. I discovered an interesting site today, https://www.cheatography.com/. This site has over 2500 cheat sheets for all manner of topics, including Office, Business, Technology, kitchen and garden, travel, and a whole lot more. The site has 17 cheat sheets relating to PowerShell as well as 35 cheat sheets relating to PHP. The most viewed cheat sheet relates to Regular Expressions (a technology I have yet to master).
The site also enables you to create your own cheat sheets.