Learn what an User Agent string is, and how they can manipulated or spoofed.
An User Agent String - or simply an User Agent - is your device's information including the make, and model, operating system type and version, as well as browser type. According to Wikipedia, "In computing, an user agent is software (a software agent) that's acting on behalf of a user. One common use of the term refers to a web browser that 'retrieves, renders and facilitates end user interaction with Web content'". When a software agent operates in a network protocol, it often identifies itself, its application type, operating system, software vendor, or software revision, by submitting a characteristic identification string to its operating peer. Bots, such as Web crawlers, often also include a URL and/or e-mail address so that the Webmaster can contact the operator of the bot.
User agents can be manipulated, and we tend to call this notion "spoofing" where in most cases spam bots, or crawlers - humans operating them - convince hosts to force content, or responses by faking the UA. Learn more about an User Agent on Wikipedia.