The [gallery] shortcode or [better_gallery] is what is used to generate galleries on posts and pages.
If you are using the gallery post type, then this is automatically included.
In addition to using the form to supply which theme you are using and whether to display captions etc, you can also supply options via the tag:
Here's a few explained.
[better_gallery template=single random=true ] This one’s nice and simple. It’s going to pull out a random single image. Super useful for homepages or maybe an about, contact or even an error page.
[better_gallery template=autoslideshow ] Another cracker for your homepage needs. This one’s is an automatic slideshow of every image you’ve added to the page. And you can throw in the random tag if your that way inclined.