Papyrus

Papyrus is an object-oriented scripting language developed by Bethesda Softworks for use in the Creation engine. Papyrus first appeared in Elder Scrolls V: Skyrim and has since been utilized in Fallout 4 and Fallout 76. Papyrus is an evolution of ObScript, the previous scripting language used in Fallout 3 and Fallout: New Vegas, with additional functionality and flexibility along with completely new syntax and workflow.

Papyrus works by receiving in-game Events and sending Function Calls. Papyrus is the driver for all quests and allows tracking of variables based on player interactions. Papyrus also handles the use of triggers, perk effect, terminal and book interactions, as well as special interactions through dialogue with characters.

Unlike the previous language, Papyrus scripts must be written in a separate text editor and compiled in the Creation Kit to be used in-game. Plugins for Notepad++ and Atom allow for use of Papyrus syntax.

From .psc to .pex
A Papyrus script starts as a plain text source document (.psc file) that can be written with the use of any text editor of choice (recommended plugin for Papyrus syntax). The .psc file must then be compiled into a form usable in-game (.pex file). Once a script has been compiled, edits must be done to the original raw .psc and then re-compiled and updated for any changes to take affect on the .pex.

Compiling
The Papyrus compiler is a command line utility that is packaged with all versions of Creation Kit that runs in editor and checks for any errors to report before turning a .psc file into a useable .pex file. The Papyrus compiler outside of the Creation Kit can be found at: ...Fallout 4{76}\Papyrus Compiler\PapyrusCompiler.exe

For a more in-depth use of the Papyrus compiler, see the Creation Kit wiki.