Hi Andrei! Above is a Gallery Block that is pointing to your "Piano/Keyboard" Gallery Page. The Gallery Block allows the full image to be displayed in multiple styles (grid, slideshow, slider and stacked) and you can edit it by doubleclicking it directly while editing the Page Content section.
I also put Spacer Blocks on either side of the Gallery Block so that you can control its size better. Click and drag the shared borders between Blocks to resize them relative to each other.
Feel free to tinker with this page or delete it! -Dylan L. @ Squarespace Customer Care