The engagement rate is a re-introduction of Google Analytics 4 (GA4), so to speak. It meaningfully measures the engagements of your website. This includes clicks, scrolls, conversions and more. So with engagement rate, you track how many people visit your page, how often users click on your links and share content. So these metrics show you how interested or engaged users are in your company.
You can also use the engagement rate to your advantage when it comes to content. Through them, you can measure, for example, whether a video was played, an infographic was downloaded, or how far a user scrolled in your content.
You can use this data to determine how helpful the included content was. For example, if someone reads a blog post in its entirety and then leaves the site, it may still have been useful. If you first jump to the video, play it, and play other videos, that content seems to have been useful as well.