An editorial calendar is a list of the content you plan to create.  The editorial calendar can also include when you plan to distribute the content and on which platform.

The benefit of having an editorial calendar is twofold.  First, it gives you a plan on all the content that you need to produce and when it needs to be created by.  But, it also lets you to see the content as an overview and not just as random things that pop into your head.

Finally, an editorial calendar help you avoid the condition on not knowing what content to create.  There are times when you might have an idea block but the editorial content gives you the option to skip being forced to think up something.  You can add ideas whenever inspiration strikes.