Where is /system script's copy-from doc ?

RouterOS Beginner Basics
1

Hello,

  1. Where can I read anything (example, doc, …) regarding /system script parameters and options ? It is missing from [1], if I’m not mistaken.
  2. Is there a reliable way to create a script from an existing file (either fetching or copying from disk or with HTTP) ?

[1] https://help.mikrotik.com/docs/display/ROS/System

Best regards