Did you know that, by default, Google keeps a detailed history of your activity on its search engine and other services when you are logged in to your Google Account? If Google has access to your device’s location settings for mapping and search suggestions it will even store your location history and display it on a map.
Part of this data-hoarding is to make Google’s predictive services more accurate by tailoring suggestions (and advertisements) to your known interests and location. Some people like having relevant material (including ads) tailored to them, but if the information collection creeps you out, you can change your Google Activity controls to clear out the stored information from your account. The company says it may still keep the data for its own purposes, but stored anonymously.
To change your Google Activity settings, go to https://www.google.com/settings/accounthistory when you are logged in to your Google Account and make adjustments as you see fit. You can delete your search and browsing history from the site, information from your mobile devices (like contacts and calendar events that use Google apps), your voice-search recordings, your location history, and your searches and viewing activity on YouTube.