pima are four very important letters for classical guitar
ists. They stand for the spanish words pulgar, indice, medio, anular.
Pulgar = thumb
Indice = index finger
Medio = middle finger
Anular = ring
The pima pattern is used for indicating how to properly finger a piece with the plucking hand.
What about the little finger? Well, it is 'c' but you'll hardly ever hear it mentioned with respect to orthodox classical guitar, since it is only really used in rasgueado or flamenco.