You can’t open an annotation as a plain text file – it’s a custom binary structure. You can visualize it on top of a surface in freeview. Something like:

freeview -f surf/lh.inflated:annot=label/lh.aparc.annot

From: <freesurfer-bounces@nmr.mgh.harvard.edu> on behalf of 1248742467 <1248742467@qq.com>
Reply-To: FS Help <freesurfer@nmr.mgh.harvard.edu>
Date: Tuesday, October 13, 2020 at 8:42 AM
To: FS Help <freesurfer@nmr.mgh.harvard.edu>
Subject: [Freesurfer] Open the .annotation file with Notepad is garbled

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Hello, FreeSurfer

Why is it garbled when I open the .annotation file with Notepad? Is there any solution? 

Looking forward to your reply