Introduced in 2017, Carousels allow users to upload multiple photos or videos to produce a "slideshow" item in their Instagram feeds. More information in this article by Refinery29.
The feature looks like this (sourced from the Refinery29 article):
Sked Social supports these posts with both images and videos in carousels.
To create a carousel post, choose 'carousel' when you are uploading from the upload posts page or 'single image'. If you choose single image you'll use the 'edit carousel' option on the post details page to add your additional frames.
You will then be able to upload up to 10 images or videos (that's Instagram's maximum number) for your carousel, and you will see in upcoming posts that the post is a carousel.
You can click 'edit carousel' to adjust the order of your content, delete one or more 'frames' or add new ones.