Flickr and Picasa are both image and video hosting websites that allow users to share photos and videos online. Flickr was created in 2004 and later acquired by Yahoo, while Picasa was created in 2002 and later acquired by Google. Both sites offer free storage and organizing of photos and videos, with paid premium accounts providing additional storage and ad-free experiences. The key differences are that Flickr offers 1TB of free storage while Picasa offers 1GB, and Flickr organizes photos into sets and collections while Picasa uses albums.