phpMyAdmin is the browser interface to your site’s MySQL database. You will not need it every day, but on the day a plugin update locks you out of wp-admin, it is the only tool that will get you back in.
Open phpMyAdmin. In cPanel, under Databases, click phpMyAdmin. It opens in a new tab already logged in. Pick your WordPress database from the left sidebar.
Find the right table. WordPress tables share a prefix, usually wp_. The two you will use most are wp_options (site settings) and wp_users (accounts).
Reset a forgotten admin password. Open wp_users, find the row for your admin, click Edit. In the user_pass field, type your new password, change the Function dropdown to MD5, and click Go. WordPress upgrades it to a stronger hash on next login.
Switch the site URL safely. If a domain change has locked you out, open wp_options and edit the siteurl and home rows. Do not run a blanket search-and-replace on serialized data — use the WP-CLI search-replace command or the Better Search Replace plugin instead.
Export the database. Click the database name, then the Export tab. Choose Quick and SQL, click Go, and you get a complete .sql file. This is the database half of any manual WordPress migration.
Repair a crashed table. If you see “Error establishing a database connection” after a host event, tick the affected tables in the database view and choose Repair table from the With selected dropdown. Nine times out of ten that clears it.
Before any of the above: always click Export first and save the dump. Database edits are not undoable.