From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Eggs (卵, Tamago) are a common food and one of the most versatile ingredients used in cooking as well as hatching. They are important in many branches of the modern food industry. Chichi was turned into an egg and crushed by Super Buu, resulting in her death. She was later revived by the Dragon Balls.
Namekians breed asexually and at any time they can create a rather large egg. These eggs oddly come out of the mouth. Piccolo Daimao is the only Namekian seen to make these eggs. The most notable Namekian egg was the one Piccolo Daimao made as he died, spawning his son/reincarnate, Piccolo.