In the context of Burp Suite, 'User-Agent' refers to an HTTP header used to identify information about the browser or client making a web request.
This header provides details about the browser type, version, and, in some cases, the user's operating system.
It is part of the information sent by the browser to the web server so that the server can tailor its response based on the client.
It's common for some websites to customize their content based on the User-Agent received in HTTP requests.
Websites may use this information to adjust their content and presentation according to the type of device or browser accessing the site.
In the context of web security testing, professionals often modify the User-Agent to assess how a website responds to different browser configurations or devices and to uncover potential vulnerabilities or security issues.