A search box or search field is a common GUI element used in computer programs, such as file managers or web browsers, and on web sites. A search box is usually a single-line text box with the dedicated function of accepting user input to be searched for in a database. Search boxes on web pages are usually used to allow users to enter a query to be submitted to a Web search engine server-side script, where an index database is queried for entries that contain one or more of the user's keywords.
Search boxes are commonly accompanied by a search button (sometimes indicated only by a magnifying glass symbol) to submit the search, although a search button may be omitted as the user may press the enter key to submit the search, or the search may be sent automatically to present the user with real-time results.
Common Features 
Depending on the particular implementation, a search box may be accompanied by a drop-down list to present the user with past searches or search suggestions. Search boxes may have other features to help the user, such as autocomplete, search suggestions, a spelling checker, etc. Search boxes are often also accompanied by drop-down menus or other input controls to allow the user to restrict the search or choose what type of content to search for.
See also