LO and LOOT – Load Order and Load Order Optimization Tool.

ITM – Identical to Master (records added by a mod that are an exact copy of records from the Vanilla game sometimes these are unintentional and need to be cleaned, and sometimes they are intentional and should NOT be cleaned).

INI – a file extension for configuration information (text file readable by notepad/wordpad).

This can include the compass, health/status/magicka bars, notifications/thoughts, custom widgets, etc.

HUD – Heads Up Display is how information about your character is conveyed visually without going to a different screen.

FOMOD – Fallout Mod Installer (also used by Skyrim mods) essentially this is an installer built into the file archive that can add choice options, additional related plugins, images, etc to assist in the installation process.

FNIS – Fores New Idles in Skyrim ( LE| SE).

ESPFE – Elder Scrolls Plugin Flagged as a Light Master.

( Read this article for more information)

ENB – is a program that uses post processing effects to create enhanced visuals in the game.

DynDOLOD – Dynamic Distant Objects Level of Detail.

DB and DG – Dragonborn and Dawnguard DLC.

CK – Creation Kit (this tool is used to both edit and create mods).

For more information, specifically about loose vs packed, read this post by the wonderful u/Thallassa)

BSA – Bethesda Softworks Archive (you will see this compressed file type in many mods it can include sounds, textures, models, etc.

AIO – All-in-One (often used to describe when a mod author has merged multiple iterations/versions of their mod(s) into one, and often can include compatibility patches as well).

Skyrim what time is dawn