When you browse the web on computers or Android devices, you can send a request to websites not to collect or track your browsing data. It's turned off by default.
However, what happens to your data depends on how a website responds to the request. Many websites will still collect and use your browsing data to improve security, provide content, services, ads and recommendations on their websites, and generate reporting statistics.
Most websites and web services, including Google's, don't change their behavior when they receive a Do Not Track request. Chrome doesn't provide details of which websites and web services respect Do Not Track requests and how websites interpret them.
"Do Not Track" isn't available for iPhones or iPads at this time.