Before we get down to the nitty gritty, you should probably learn how to install a Mod into your game.
The Sims 4 makes it easier than ever to install mods: simply download the mod in question, unzip the files (they will typically end in .package), and then drag and drop them into the "Mods" folder, which is already located in your Sims files (navigate to Documents *This hub will be regularly updated to include the newest/coolest mods! Fans have been creating Mods and sharing them online since the Sims 2 was released.
Though all of these Mods have been tested and should work functionally with your game, be aware that 3rd party content could potentially cause damage to your game.
Always download from trusted sites/users whom have tested their content before sharing, and always be sure to backup your game files BEFORE installing Mods and other CC.
If you do run into any issues after installing a Mod, remove the Mod from your game and consider telling the Mod's creator about the issues you ran into.
I've only used this mod briefly, but it's a BIG one in the Sims community.
Some Mods are much less complex- just restructuring the regular game files to add in or change things (like a Sims 3 Mod which allows Late Night bars to stay open 24 hours instead of closing at 2 am, or, the most famous Mod of all- the one that removes the pixelation when Sims are nude and replaces it with body parts).
Whether you're new to the modding world, or can't run a Sims game without CC and Mods, these are 5 essential Sims 4 Mods that every Simmer will want to add to their game!
This mod allows your neighborhood to grow and thrive without your direct interactions.
A lot of Simmers live by this mod, and I can see why: the vanilla game can feel a bit static in the fact that the other Sims in your neighborhood don't do anything without you; now with MC Command Center, life goes on, whether or not you play each individual household.
Sims can now get married, have children, find jobs and basically live their lives, even if you aren't playing with them.
You can also add in additional modules, which will allow the game to clean up your neighborhood, by deleting homeless Sims, ghosts, will allow you to set default makeup and clothes on townies, and a whole bunch of other options.
"Mods", short for 'Modifications' are user-created files which modify or add more to the regular Sims games.
The options for Mods are pretty diverse- I've seen everything from a Mod in Sims 2 which added horses to the game (and yes, Sims could even ride them- and this was way before the Pets expansion pack added horses to Sims 3), to a Mod for The Sims 3, which added in a working Ferris Wheel.