Code coverage is nothing but testing the whole code once to 
checking whether it is up to testing or not.

Code coverage is a measure for white box testing.It is used 
to determine what percent of structure of code is executed 
by exercised test cases.
Below are the types of code coverage.

1)Statement Coverage.
2)Path Coverage.
3)Decision Coverage.
4)Condition Coverage. 

for instance Statment coverage is percentage of statements 
executed by designed test caes.