This is called the Portfolio Section in the theme.
Use it to display your best visual content.
To set it up, go to DASHBOARD > APPEARANCE > CUSTOMIZE > PORTFOLIO SECTION.
Here, you can choose to turn it off in the Settings tab, or set the number of items to display in that space.
Content is where you edit the title, Single Page makes sure that all your portfolio items are displayed in a full width page with no sidebars and then you have Color options too.
Once you’re done with this, navigate to DASHBOARD > PORTFOLIO > ADD NEW to create new content.
To edit the existing ones, go to DASHBOARD > PORTFOLIO > PORTFOLIO and you’ll see them all listed together.
Portfolios are created in the same way that pages are. You can format them in whichever way you think is appropriate, however make sure you upload a featured image (recommended size 500 x 500 pixels) as this is what will be displayed on the homepage.