Every WordPress site needs a theme to pull content from the database and display that in a design. And theoretically you could run a site with just a theme and nothing else. But that site would be very limited without the addition of plugins. Plugins add extra functionality to your WordPress site over and above what comes with WordPress core. Everything from a booking calendar or animated slider to a full-featured learning management system or online marketplace—you can add them all to your site with plugins.
How to Create a Custom WordPress Plugin From Scratch?. The Complete WordPress Developer Course 2022 [Videos].