Adware:W32/BTB.A is detection for an adware toolbar.
The software used to develop this toolbar can be utilized for non-malicious and malicious purposes, such as redirecting searches to unsafe sites.
Additional Details
The toolbar redirects searches to links found in an XML file.
A malicious "developer" can modify this XML file and insert links pointing to unsafe sites. This toolbar can then be used to compromise the user's privacy, such as browsing habits that other third-party operations, such as advertising companies.