The physical interface(s) or form factor(s) are Apple proprietary. The different SSDs have 6+12/12+16/8+18/7+17 pins. The electrical/logical interface is PCIe 2.0 2x or 4x (everymac.com also mentions SATA for some older MacBook Airs).
Several adapters for different MacBook (Air) SSDs are available here.
Example: MacBook Air Mid 2013 SSD to PCI-e 1X

I haven't been able to find an adapter for the MacBook Air Early 2015 SSD there. The latest MacBook Air uses a proprietary PCIe 2.0 4x instead of a proprietary PCIe 2.0 2x interface like older MacBook Airs.
I don't own a PC, so none of the pre-2018 links lead to anything I can use. Has anyone found a solution that works in OS X?
– Fran K. Oct 17 '18 at 17:50R+Command), then use diskutil in terminal to access the disk. The disk will not show in Disk Utility, you have to use terminal. Watch video for demo: https://youtu.be/47--98JReaU?t=45 – user160357 May 28 '22 at 03:34