WordPress is a great platform and has surprisingly flexible permissions. However, by default, the permissions system keeps to the WordPress philosophy of "Decisions, not options". This means that there are 5 user roles by default: Administrator, Editor, Author, Contributor and Subscriber. But you're not able to edit these roles without installing a plugin.
In this guide, I'll introduce 5 of the best plugins for customizing the permissions on your WordPress site. These plugins will allow you to customize the 5 default roles, and also create your own rules and permissions.