Carbon 12 has 6 protons and 6 neutrons. Carbon 14 has 6 protons and 8 neutrons.
Carbon 12 is abundant in the environment, accounting for 98.89% of all carbon and is a stable isotope of carbon. Carbon 14 accounts for only about 1 trillionth of all of the carbon on Earth and is radioactive, with a half life of roughly 5700 years, which makes it good for use in dating fossils etc