This is particularly important if you are adding POSTS to your website and they are quite long. The icon highlighted in the image above is the Insert Read More tag.
You use it so that when your post is displayed on your news page, you only see the top part of it. When the “Read More tag” is detected the post stops being displayed any further and read more… appears as a link.
Clicking on the link causes the Post to open full screen in it’s entirety.
Why is that a good idea?
Mainly because people do not read websites, they browse them. As such if they have to plough through several screens worth of text about a news item that they are not interested in they may get bored and leave your site.
If you insert the read more tag (which I do on most of the posts on this site) all you will see is the first paragraph or two. You can scan that and if you are interested read more, if not it is easy to skip down to the next one.
So remember, always use Read More if you have a longish post, particularly if your site is one of the newer ones using Divi.