Instagram is a photo and video sharing social media platform with over 400 million active users worldwide. The app allows users to take photos and videos, apply filters to images, and share content publicly or privately on Instagram as well as other social media like Facebook and Twitter. The summary outlines how to download Instagram, set up an account by providing email/phone number and personal details, and post a first photo by choosing an image or taking a photo, selecting a filter, adding a caption, and sharing the post.