Tech companies like Apple, Amazon, and Facebook use AI and machine learning within our devices such as phones and computers to track us. Machine learning is a group of AI that gathers large amounts of data then makes a prediction based on that data. And as time goes by, AI learns and these predicitions and gets more accurate.
Nowadays, AI has perfected its abilities to predict what products you would be interested in buying or seeing on social media. In order to do this they gather large amounts of data and analyze it to make a good guess on what you would be interested in. Some of these companies have access to files in your phone like text messages, photos, etc which is one way in how they gather their data. Therefore, for these big tech companies AI is a very useful marketing tool for them. The chart below shows that most big tech companies are using AI to gather information and advertise products.
You can be instantly recognized in any Facebook post due to DeepFace, an AI engine used by Facebook. This AI is so advanced that it is claimed that the facial recognition is more precise compared to humans. However as of now this is being used positively to protect users from identity theft and impersonation.
Sources
The 10 Best Examples Of How Companies Use Artificial Intelligence In Practice
Are You Addicted to Social Media?
"How Tech Companies Track Your Every Move And Put Your Data Up For Sale"