I’ve always thought of the WP Admin as the back side of a WordPress site. It’s where you will build and manage your site. It’s the heart of WordPress. It’s like a web site that lets you make your web site.
As you’ll see, with any WP site you will need a user name and password to login. Once you’re in you’ll be able to manage your site – add or edit pages and posts, change a theme, add or remove a plugin. All that and more is what the WP Admin is for.
The web address to find where to login is easy to remember. in almost all cases it will be
that takes you to the login screen.
Word To The Wise Which Means You
Some tine soon (Summer of 2018?) WordPress will introduce its new page editor k/a Gutenberg. I have videos on it too or read "WordPress In 2018 Is Getting A New Page Editor And It’s Called Gutenberg."