There are 2 types of galleries. First one is a default as strip of images. And second gallery is a module with Hero image, and 4 images under. Lightbox provides 2 different screens. The first one is a single picture view and the second one is an overview across all images in the gallery. Overview is accessible by clicking on Gallery preview button.
We will not go through the authoring process of default gallery as it is a basic functionality of any WordPress. Please see only the differences in the gallery creation flow.