Top Wordpress plugins grouped by what they do
Wordpress is a famous CMS, but it's far from "complete" out of the box. Wordpress is born to solve the "blog" problem, so the native CMS provides only blog functionalities.
Over the years, Wordpress started to be used for building websites that are not traditional blogs, and this trend changed the ecosystem of the platform, which saw emerging plugins, each adding specific functionality to the CMS. Nowadays, the ecosystem is the platform!
Why do you need Worpress plugins?
Your website needs good SEO tools? It's better to use a dedicated SEO plugin ...
Your website is for a business that sells services, and each service has the same structure of information? You need dynamic data plugins...
Your website lets the user contact you with a form? You need a form plugin...
You... get the idea!
The Wordpress CMS capabilities of the early days are pretty much the same as what Wordpress offers today. The ecosystem is the platform. The platform is made of plugins. You need to know them (and do not abuse)!
Collection of Plugins
Here is a list of the most used Wordpress plugins (based on my perspective).
I update the list regularly.
You can add your own plugins to the list by following the instructions that you find in the link.