A mechanic is someone who uses tools to fix machinery. There are many different types of mechanic, but the kind that is most commonly associated with the word is an auto mechanic - someone who fixes cars.
Midwives offer care to pregnant women through their pregnancy, the delivery of their babies and for some time after the birth. Compared to obstetricians, midwives generally take care of women with low-risk pregnancies, and strive to help women have a natural birthing experience and try to intervene as little as possible.
A monk is a man who lives a strict religious life, usually as a member of a religious or monastic group.