Some of the underlying details (mostly non-technical): https://www.imageidentify.com/about/how-it-works

The function in the Wolfram Language is called ImageIdentify (obviously): http://reference.wolfram.com/language/ref/ImageIdentify.html

A blogpost from Stephen Wolfram about this site and related topics: http://blog.stephenwolfram.com/2015/05/wolfram-language-arti...