What is a Parson? How is the Parson different from the Frair or Monk?

A good religious man, A Parson of a Town,, who, although poor in goods, is rich in holy thought and work. He's a learned man, who truly preaches Christ's gospel, and devoutly teaches his parishioners. He travels across his big parish to visit all of his parishioners, on his feet, carrying a staff in his hand. He is a noble example to his parishioners ('his sheep', as they are described) because he acts first, and preaches second (or, in Chaucer's phrase, 'first he wroghte, and afterward he taughte'). The narrator believes that there is no better priest to be found anywhere.