@gamefu91 Crying is essentially convulsions of the thoracic cage and diaphragm, accompanied by tears and vocal sounds. These convulsions are stronger than normal attempts to breathe, and it takes greater than usual strength to inflate the lungs for the first time (think of a brand new balloon compared to one that has been inflated before). Mature lungs have a substance called surfactant in them that prevents them from totally deflating, and hence making breathing easier, but for it to form its surface tension the lungs need to be inflated first.
In @Judi‘s case, they primarily need to clear the lungs of amniotic fluid that may have gone into the airways (the trachea and major bronchi are held open by cartilage), but also to check for conditions such as meconium aspiration and hyaline membrane disease. Basically, a good cry is a clinical confirmation for the obstetrician that the baby’s respiratory system is healthy. If the baby doesn’t cry it isn’t a big deal unless it is accompanied by other signs and symptoms, because as with @Judi the doctor will make them cry before the umbilical cord is severed.