What is the difference between separate property and community property?

While many of our American laws are based on English common law, the concept of community property is based on Roman civil law, which may be why it seems unusual to us when compared to other areas of law. It is based on the concept of a community which is created when two parties legally marry or register as domestic partners, and it treats each member of the community as equal regardless of the economic benefit that member contributes to the community.