The WordPress menu has some standard options plus any that have been added by plugins. These are the most commonly used ones:
Use the Updates option to update WordPress, plugins and your theme.
Posts are the type of page you'd use for blogs posts, news, etc. These can be divided up using Categories and Tags, which make it possible to arrange posts on the website, and offer search options to visitors.
Media includes images, photos and also downloadable files like PDFs. Use Library to view all existing media files.
Pages works in a similar way to Posts but is designed for adding the main content pages to your website.
These are the extra ones you'll see if you have Divi Builder:
Projects are special type of page you can use for types of pages specific to your website, such as case studies . These can also be divided up using Categories and Tags, which make it possible to arrange these page on the website, and offer search options to visitors.
The are the options specific to the Divi Builder. These are used to manage things like the website menus and other configuration options.