This is a Text & Full Image block. Click on this text to start editing and enter your own text with some basic formatting. Just click anywhere outside the text box when you're done to continue working on the rest of your page.
Hover your mouse over the image opposite to show the image toolbar. Image Settings lets you choose an image from your library, or upload a new one, and change related settings. On this block the image will size automatically based on the height of this content, filling the available space.