The second one ( Master Boot Record) is old, from the 80's DOS 2, for old PCs. Booting is not an issue for my use of this flash drive.
I know the first one ( GUID Partition Map) is for booting modern Macs. When using Disk Utility 16.3 with macOS Sierra to format a 'thumbdrive' USB 3 Lexar flash drive (64 gigs), when I choose a Format of ‘Mac OS Extended (Journaled)’, I get a list of three Scheme items: