Where can I find what Apple considers "Other" storage with specificity? I have over 130 GB being used - half my MacBook Pro

It is known that macOS Storage Management doesn't always show the correct amounts for the various sections. The important part is how much free space you have overall. Only delete items within your user folder(s) and be especially careful removing items from the "~/Library" folder as well. You should never delete anything from the other Library folders as you may break macOS (this is much more difficult to do today with the extra security preventing modification to system areas).

Boot into Safe Made so that macOS will delete any temp and cache files for you. Plus you can delete or clear your browsers' cache from within the browser itself (usually under the "Privacy" settings/Preferences with the browser).

Have all your backups completely transferred to your external media? APFS file system snapshots used by various backup solutions will retain all data even if those files have been deleted. Once the backup has completely transferred those APFS snapshots should be automatically deleted. macOS will also create an APFS snapshot when updating macOS as well. Most APFS snaphots will be automatically deleted after a week (not sure about snapshots for backups). You can thin or delete APFS snapshots using information in this article:

https://derflounder.wordpress.com/2018/04/07/reclaiming-drive-space-by-thinning-apple-file-system-snapshot-backups/

Storage

• Other: Contains files that don’t fall into the categories listed here. This category primarily includes files and data used by the system, such as log files, caches, VM files, and other runtime system resources. Also included are temporary files, fonts, app support files, and plug-ins. You can't manage the contents of this category. The contents are managed by macOS, and the category varies in size depending on the current state of your Mac.

       https://support.apple.com/guide/system-information/see-available-storage-space-syspf9b375b9/11.0/mac/11.0

https://support.apple.com/guide/system-information/optimize-storage-space-sysp4ee93ca4/11.0/mac/11.0

Welcome!

What mac OS version? In Big Sur, the system is supposed to take care of it:

See used and available storage space on your Mac - Apple Support

I just checked a new M1MacBook Pro I am setting up for a friend and it showed 15GB "Other" after running for ten days. After restarting, it shows 9GB. See if a restart reduces the "other" in your computer.

If you are not running Big Sur, it could be from third-party apps. So-called "cleaning" apps have caused that, as have printer software that fails to clear print job caches. I've seen reports of Google Chrome load a computer with temp files and helper files as well.

So we need to know your macOS version to offer more specific advice.