Adding content to your site is an easy process no matter whether you’re creating a Post or a Page. The procedure for both is almost identical. Apart from how they display on your site, which was described earlier, the other main difference is that Posts allow you to associate Categoriesand Tags whereas Pages don’t. What’s the difference between categories and tags? Normally, Tags are ad-hoc keywords that identify important information in your Post (names, subjects, etc) that may or may not recur in other Posts, while Categories are pre-determined sections. If you think of your site like a book, the Categories are like the Table of Contents and the Tags are like the terms in the index.
With WordPress 5.0, a brand-new editing interface has been introduced. The new editor is called the Block Editor, although you may also know it by its development codename, Gutenberg. The editing interface has been rebuilt to make it easier to create media rich Pages and Posts and to provide you with more flexibility.
Starting from WordPress 5.0, the Block Editor will be the default editor whenever you're creating a new Page or Post. However, if you wish to continue to use the old (TinyMCE) Classic Editor, you can do so by installing the Classic Editor plugin. The Classic Editor plugin will allow you to disable the new Block Editor and instead, will provide you with the same editing interface that you've been using prior to WP 5.0. The Classic Editor can be downloaded from the Plugin Directory on the WordPress.org website, or you can install it directly onto your site using the Plugins > Add New menu option and then typing in ‘Classic Editor’ (without the quotes) in the Search Plugins… field.
If you find that your theme doesn't work properly with the new Block Editor, or maybe some of your existing plugins don't work as expected, then it's highly recommended to install the Classic Editor plugin to revert the editor back to the same interface you were using prior to WordPress 5.0. If, sometime in future, you change themes or plugins and decide you want to use the new Block editor, then you can simply deactivate the Classic Editor plugin.