A digital signature is cryptographic proof attached to software that identifies its publisher and shows the content has not changed since signing. Windows checks signatures on driver packages before trusting them.
In practice
On 64-bit Windows, kernel-mode drivers must carry signatures acceptable to Windows to load in normal operation. Packages distributed through Windows Update are signed through Microsoft's programs, which also influences how Windows ranks them against other matching packages.
Common confusion
A signature is not an endorsement that a driver is bug-free or ideal for your device. It also differs from a certificate of compatibility testing, although some signing paths involve testing. Signed simply means origin and integrity can be verified.
Why it matters to readers
When a driver source cannot provide a properly signed package, that is a strong reason to look elsewhere. Reference maker sites and Windows Update provide signed packages as standard.
A closer look
Signatures carry timestamps so that a package signed while its certificate was valid remains trustworthy after the certificate later expires. That detail prevents perfectly good older drivers from suddenly failing. Separately, Windows offers a test-signing mode for developers, which is not intended for everyday computers and displays a watermark on the desktop while it is enabled.
