When you install a WordPress gallery plugin that comes with a lightbox, clicking one of the thumbnails in the grid will display the full size image on top of the content.
A lightbox can also be used with a single image.
Each lightbox plugin works a bit differently in terms of how full images, image titles, navigation, etc. display.
Many gallery plugins also offer social sharing and download options within the lightbox.
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Thank you very much, Abadi. Glad you find it helpful (: