What scripts and executors actually are
A script is a small piece of Lua code that adds features to a Roblox game, like auto farming, ESP (seeing players through walls) or a menu full of toggles. Roblox doesn't let you run your own code in other people's games, so you need an executor: a separate app that attaches to Roblox and runs the script for you.
Most scripts on Rscripts are a single line that starts with loadstring. That line downloads the real script from its creator when you run it, which is why scripts can update without you copying anything new.