Young Earth Creationism
The idea that the Biblical book of Genesis is literally true. It stems from the assumption that all of the Bible is literally true. It includes the assumption that by adding up the ages of various Biblical characters that directly descend from Adam, the age of the Earth can be calculated to be between 6,000 and 10,000 years.
Old Earth Creationism
The idea that God created the universe, but that the book of Genesis should be interpreted figuratively whenever directly contradicted by physical evidence. This means, for instance, that the Earth is many millions of years old, but God still managed the entire process of its creation and development.