WordPress Hierarchy – Important Files and Directories

wp-config.php file contains all information about your database connection and some salts which are used for password generation
index.php handles all the requests on your wordpress blog
wp-content/themes contains all the themes installed in your blog
wp-content/plugins contains all the plugins installed in your blog
yourblog.com/wp-login.php or yourblog.com/wp-admin/ can be used for logging into wordpress backend
wp-content/uploads contains all your file uploads including all the images in media. They are usually categorized in folders like 2018/month_number (08 09 etc)
users table is used for storing all your user details like username, first name, last name, email and password
other details about users are generally stored in usermeta table
options table is used for storing all the blog settings. generally first and second row in this table contain the url of your wordpress blog.