I believe you have to be of a certain age (like not older than 30ish) they give you a fertility treatment or two to produce more eggs, so that when they harvest them (through the doo da), they will have more to harvest and freeze for the potential recipient.
She leaves them in a basket or hides them on your front lawn, lol. (Just kidding. Wrong gift giver.) Her eggs, as many as she chooses, are removed from one of her ovaries while she is under anesthesia. The doctor uses a small syringe-type instrument to do this. It's a very delicate procedure. Once the eggs are removed they are observed under a microscope for defects & overall quality. If the eggs are healthy they are specially frozen for fertilization later. For her future needs or others. Meaning she donates them to another woman or couple in need of healthy eggs so they can create their own baby. It's far more complicated than I explain but this gives you a general idea.