From Wikipedia:
User Account Control (
UAC) is a technology and security infrastructure introduced with
Microsoft's
Windows Vista and
Windows Server 2008 operating systems, with a more relaxed
[1] version also present in
Windows 7 and
Windows Server 2008 R2 . It aims to improve the security of
Microsoft Windows by limiting
application software to standard user privileges until an
administrator authorizes an increase or elevation. In this way, only applications trusted by the user may receive administrative privileges, and
malware should be kept from compromising the operating system. In other words, a user account may have administrator privileges assigned to it, but applications that the user runs do not inherit those privileges unless they are approved beforehand or the user explicitly authorizes it.