A Mac address or media access control address is a unique digital identifier of your bike whereas the frame (or serial) number is the unique physical identifier.
You can find the frame number underneath the bike, below the bottom bracket. You should find a sticker with a QR code and a code starting with CBFM (CowBoy FraMe).
You will also be able to find the code in the Cowboy app after you've activated your bike. Go to Settings --> Advanced --> It's the code under "Serial Number".
An example of a frame number is CBFM18A00967
When receiving your new bike, the Mac address is noted on a wrap which you can find on the frame of the bike. You'll need to scan this QR code to activate a brand new bike.
When your bike is activated, you can find your Mac address in the Cowboy app. Go to Settings --> Advanced --> It's the code under "Mac address"
An example of a Mac address is F7:0B:04:08:78:28