What do the letters in the brush names mean? (Brush Type Key)
Each brush has a one or two letter key code in it’s name. These help identify the brush type and are as follows:

G (Gouache)
CH (Charcoal brushes)
E (Eraser)/Users/tkeiger/Creative Cloud Files
FI (Fill)
FX (Effect brushes)
H (Cross Hatch)
I (Ink brushes)
P (Pencil)
MI (mixer/blender)
NM (Natural Media – This one covers a lot of brushes that don’t fit into other categories)
O (Oil)
OI (Oil Impasto)
S (Specialty)
W (Watercolour)