WordPress 5.7 has 66 enhancements and feature request along with 127 bug fixes.

A few of the highlights:

• For the site content creator: more updates to the block editor to make it easier to add in and work with content, and default lazy-loading iframes.
• For the site administrator: a new feature that allows website administrators to manually send a reset password link to existing users, as well a simplified way to meal the http to https switch.
• For the site developer: new post parent functions that will reduce some of the logic needed/currently used in themes and plugins, and a number of REST API changes.

You can read more by looking at the release notes: https://make.wordpress.org/core/2021/02/23/wordpress-5-7-field-guide/

You can also see a complete list of changes: https://core.trac.wordpress.org/query?status=closed&resolution=fixed&milestone=5.7&order=priority

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.