Beautify vs. format
The same thing: both re-print code with consistent indentation and line breaks. This page uses Prettier with the options you choose — semicolons, single or double quotes, print width.
Unminifying code
Beautifying minified code restores the structure, but not the original names: if a minifier renamed tickets to t, it stays t. Short-circuit tricks like !0 for true are also kept. That is usually enough to follow what a script does.