What does the -Transform do in this example

Hello everyone. New to the tool and site. When playing with the example files I wasn’t sure what -Transform does? I assume it transforms the .msi to .mst, but if so, why?

Thank you!

[string]$installPhase = ‘Installation’

	# Install the base MSI and apply a transform
    Execute-MSI -Action Install -Path 'Adobe_Reader_11.0.0_EN.msi' <strong>-Transform</strong> 'Adobe_Reader_11.0.0_EN_01.mst'
    # Install the patch
    Execute-MSI -Action Patch -Path 'Adobe_Reader_11.0.6_EN.msp'

A transform is basically a customization file for the MSI. More info can be found here, https://msdn.microsoft.com/en-us/library/windows/desktop/aa367447(v=vs.85).aspx. So that command is just applying the customizations to the instalation.

I don’t create MSTs very often, but when I do, I usually use Orca from Microsoft. For Adobe Acrobat Reader example specifically, you’d use the Adobe Customization Wizard to create that MST.