This is the first paragraph of text in your post. This text will appear as the description of your post on all blog feeds throughout your site. If you would like an alternate description to appear instead, open the Blog Properties Panel to the left, expand the Display tab and enter new text into the Featured Description area.
Did you know that you can also add any other element that you would normally use on your websites by simply opening the Elements Panel to the left and dragging and dropping the element you want onto your canvas? You might notice that in the dropdown for Blog in the Element Panel there is a Blog Feed element. Try that out to see how you can customize different feeds on your site to show different categories.