This post by Benedict Evans first digs into the idea of artificial intelligence, then looks at the efforts by Apple and Google to get a sense of who is doing what.

So you can say to your phone: ‘show me pictures of my dog at the beach’ and a speech recognition system turns the audio into text, natural language processing takes the text, works out that this is a photo query and hands it off to your photo app, and your photo app, which has used ML [machine learning] systems to tag your photos with ‘dog’ and ‘beach’, runs a database query and shows you the tagged images. Magic.

If you have even the slightest interest in artificial intelligence, neural nets, speech recognition, etc., this is worth the read.