# Core concepts
# Stories and Story Groups
Stories are full-screen media that can be images, GIFs, or videos. Regular image and GIF stories are displayed for 7 seconds, and videos are displayed for 15 seconds.
Video streaming can be enabled in a special story type called IVoD (Interactive Video on Demand). They can be up to 30 minutes long.
Each story has a unique identifier, a title (set to the story group’s title by default), a media component, an index to the position where it is in the story group, and seen/unseen information to enable end-users to continue viewing the story group where they left off.
Story groups are used to categorize stories. A story group contains up to 100 stories. Since IVoD is a special type, an IVoD story fits in a single-story group with no other stories in it.
Each story group has a unique identifier, a title, an icon (shown in Storyly bar), an index to the position where it is in the Storyly bar, seen/unseen information to differentiate the completely watched stories and the stories in it. Story groups in Storyly view are dynamically ordered. When a user watches all stories in a story group, that group is placed at the end of the bar unless it is pinned.
Multiple Storyly views can be added to various pages of your apps. Multi-instances provide different stories and story groups in different places.
Buttons or swipe-ups can be added to stories in order to redirect the end-user to an in-app page or outlink.