[Closed] Difference between Forge mod and spigot plugins.
Plugins, which can be run off of CraftBukkit/Spigot/Paper, are used to change and/or enhance existing Minecraft server content. They are used server-side only, meaning that players aren't required to take any extra steps in order to connect to a server running plugins. Some of the most popular plugins you've likely heard of are "Essentials", "GriefPrevention", and "WorldEdit".
Mods, which are typically run off of Forge, are used to add new items/features to the Minecraft and/or enhance the existing gameplay. Mods are often required client and server-side (such as "Biomes O' Plenty"), though some mods are built as client-side only (such as "Optifine" or "Damage Indicators"). Mods can also be grouped together to create what is known as a modpack (such as "All The Mods 3" or "Sky Factory").
Unfortunately, mods and plugins tend to not want to play well together, so it's unlikely you'll be able to run a server with both successfully. However, it is possible, especially if you're willing to run an older version of Minecraft (1.7.10 or 1.6.4 are the most common for plugin/mod compatibility).