Slideflickr is an online tool that allows users to create custom slideshows from their Flickr photos and embed them on websites. It works by allowing users to copy and paste a Flickr URL, specify parameters like tags or favorites, and generate HTML code. The tool fetches the images from Flickr using its API and displays them as a slideshow with options to customize features like background color, logo, and music. Over 41,000 slideshows have been created with Slideflickr, which is used worldwide to display photo slideshows on websites and as alternatives to other media players.