Edit m4a file properties...

Firstly, am I correct in thinking that '*.m4a' files are files bought/downloaded from the iTunes store?

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(That said, some of my m4a files are files ripped from CDs using iTunes - That's a different question, but why do some files ripped from the same CD at the same time appear as m4a files and some as mp3s???)

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If my understanding of m4a files is correct, then I don't seem to be able to edit the file Properties in Windows/File Explorer, as I can with '*.mp3' files - I haven't tried editing every one of my m4a files, but every one that I have tried to edit will not allow me to do so!

When I say 'edit' the file, what I mean is - when I open a music sub-folder on my HDD in Windows File Explorer (Windows 10), the default fields I have displayed are... 'Name', '#' (Track Number), 'Title', 'Contributing Artists' & 'Album'. Some of these fields, for some of the tracks on my HDD, are blank or contain incorrect information - this is what I want to 'edit'.

For most (mp3) tracks, I simply 'Right-click' the track (File) and then select Properties>Details (tab). I can then click any field in the Properties dialog box and edit/enter the information as I wish. If I can't, it usually means the 'Read-only' box on the General tab in the Properties dialog box is ticked. Unticking it usually makes the fields on the Details tab editable - I've checked this with the m4a files, but it makes no difference!

Is there a way for me to attach (a) screenshot(s) to this Post, to illustrate the issue?