This refers to MTP (Media Transfer Protocol). Very old Android devices (with Android 2.x) used to pass-thru the SD card to the host as a USB Storage Device, but

This refers to MTP (Media Transfer Protocol). Very old Android devices (with Android 2.x) used to pass-thru the SD card to the host as a USB Storage Device, but that solution was clunky as it requires detaching the SD card from the phone itself. MTP is file-level protocol and you can continue accessing all files on the phone at the same time as accessing them from your computer. MTP is part of the "Windows Media" framework and so works out-of-the-box in Windows. Linux supports it for 8+ years through GVFS and KIO, while Apple doesn't to this day.