WordPress 5.1 focuses on performance and site health.

WordPress 5.1 focuses on performance improvements to the block editor as well as adds in a few nice touches to help site administrators focus on security and performance with the addition of a nice set of functions/features.

• PHP Site Health (notification if you are running an out-of-date version of PHP.)
• Fatal Error Protection (say goodbye to the white screen of death if a change is made that triggers a fatal error). WordPress is now able to detect most of these errors and recover from them.
• Plugin PHP Version Notices (When looking for plugins to install, WordPress will now disable any plugins that require an incompatible version of PHP so they will not install.)
• Custom Definable Debug Error Log (define( 'WP_DEBUG_LOG') Now you are able to define your custom error log path vs. the default /wp-content/debug.log.

You can read more by looking at the release notes: https://codex.wordpress.org/Version_5.1

If you have not done so already – download the update or simply use your existing installation of WordPress to update your site. Either way – this is an excellent time to make a backup copy of your site(s) before upgrading.