Search History: Search history refers to the information many search engines collect and store on a search user's research habits, such as past websites visited. While some users distrust this data collection, this is often used to make information more easily findable. In many cases, search engines will determine what a document is and how much they trust a domain based on their aggregate usage data. However, in popular context, it is typically more commonly recognized as a method used to better target advertisements at users.
Google allows users to view and delete their search history through a number of basic steps. Users can also turn off their search history so their results and actions will not be visible on their Google History page. However, Google has stated that they do retain a separate log system to prevent spam and abuse and improve their services. Deleting items from your search history therefore only means that they are no longer associated with your Google Account. Fortunately, not every user's search data is retained in this separate search log.
Search history can also be occasionally prevented or disabled by opening an incognito window, a feature of Google Chrome. Other search engines also have similar tools and search history accounts to allow their users to delete and control data, though user information is constantly being collected on the user to improve results.