Content-based image retrieval is a system which searches images in database by using the image contents. For example, a user can provide an image to the system as a query, and the CBIR system will analyze the image content and search for similar images.
This technology is widely used on the Internet. For example, the two giant search engines, Google and Bing, also provide users the interface to use CBIR system.
It is very simple. We click on the camera icon, and select an image to upload. Google will analyze the image and return relavant search results.