GarageBand Alternative for Windows Users

The short version

GarageBand is free on Apple devices and not on Windows.
Audacity is free, open source and runs on Windows.
DaVinci Resolve is free and has a dialogue page, built for video.
Tunedzy is a Windows app for cleaning and finishing voices.

The Windows options

Audacity: free and open source, a good manual editor for voices.
DaVinci Resolve: free, with a dialogue page for speech; built for video.
Tunedzy: a Windows app for cleanup, editing by transcript, Multitrack and loudness.

Which to pick

For basic voice editing, Audacity. For a video project with speech, DaVinci Resolve. For cleaning and finishing a voice to a loudness target, Tunedzy. The GarageBand comparison covers the music side.