Or she may express her milk to feed her baby at a time when she cant physically feed by breast,or someone else has to feed the baby for her when she isn't there to do it. Sometimes the father may want to feed the baby for bonding purposes, so by expressing milk with a special hand pump or an electric version it can then be bottled for anyone to hand feed by bottle with breast milk in it.
she is breast feeding. it does not always mean the baby is crying just that the baby is hungry when they are small their mother is their nutrition source. also for babies it can be a comfort thing to be near their mother. :)
There is a devise called a breast milk pump that is used to extract milk or it can be done by hand. The milk can be saved in bottles and put in the 'frig' or freezer. Then others, like a babysitter, or dad can use it to feed the baby when mom isn't there.