A mandola is a larger and lower-pitched version of a mandolin. As the name suggests, it is to the plucked string orchestra what a viola is to a regular orchestra.
A mandola can be tuned CGDA (which is the same tuning as a viola). However, in this part of the world most mandola players (the MMO mandola players included) play at a lower pitch (GDAE – like a mandolin but one octave lower). This is also known as an octave mandola. Our arrangements tend to assume the mandolas are tuned GDAE.