The difference between common law and civil law is primarily a location issue. Both of these laws are born out of decisions made by judges and other ruling bodies.
Common Law is applied throughout a nation. Civil law is determined at the state or province level.
Statutory or written laws often prevail over both types of common and civil law, but not always.
An example can be found in whether or not a small business with no employees has to buy workmans’ comp insurance.
This example involves a partnership with no employees. The business is in repair and home improvement. These 2 contractors do installation work for a major Home improvement center and also do warrantee work on modular homes for a Home manufacturer.
By all indications in the statutory laws for their state, they are not required to have workmans’ compensation. However, if anyone they do work through (like the manufacturer or the improvement store) requires that they have to have it when they work for them, then the contractors have to get it.
If they didn’t get it and had to go to arbitration to settle disputes over responsibility, the workmans’ comp judge can decide in favor of whom he deems appropriate. What the judge decides is likely considered to be civil law.
A good book to get for understanding legal terms is Black’s dictionary of legal terms.