Realms come with preinstalled plugins to allow for additional customization. The plugins have been chosen to offer as many features as possible while keeping realms performant and lag-free.
Essentials is the essential plugin suite for Minecraft servers, with over 130 commands and features.
Learn more at https://essinfo.xeya.me/commands.html.
WorldEdit is an easy-to-use in-game Minecraft map editor. Through a combination of commands and brushes, you can sculpt your world or simply perform numerous terraforming tasks.
Learn more at https://worldedit.enginehub.org/
WorldGuard has a host of functions for server owners, server map makers, regular survival servers, and everyone else in between.
Learn more at https://worldguard.enginehub.org/
LuckPerms is a permissions plugin for Minecraft servers. It allows server admins to control what features players can use by creating groups and assigning permissions.
Learn more at https://luckperms.net/wiki/