Good Ol' Scoundrel
That's quite a long answer. Making it short: Star Wars like Vikings, sort of. It's a culture of warriors, whatever species they are, that loves to battle and war. This is how they achieve honor and so on. They are basically warriors that long for combat and battle. It's not a species or a race, it used to be in ancient times but later in the Star Wars universe that species went extinct and instead it turned into a culture. You can be Human (most of em actually are currently), Trandoshan, Wookie, Sullustan, whatever race you want, it doesnt matter in the end though a Mandalorian first classifies himself as a Mandalorian then a Wookie/Human/Sullustan/Anzati or whatever race they are. In the Mandalorian culture no one cares what blood you are, you can be a human father to a wookie and so on. As the Mandos say - Family is more than blood.