The Gallery block allows you to easily add multiple photos and automatically arrange them in a gallery. You can control the number of columns and the size of the images in the gallery.  The Gallery block can be added to a page by clicking on the Block Inserter (+) icon and selecting the Gallery block.  Alternatively, you can type /gallery and press Enter.

1. Click on the Block Inserter.
2. Click or drag the Gallery block into position.
3. Once in position, select the images for your gallery as illustrated in the animation below.
   
   

For a larger image, right-click and select Open Image in New Tab

References

• The Gallery Block (wordpress.org)
• Image Accessibility (W3C Initiative on Images)