Candidate key = Key = Minimal Superkey? I got a little confused by all these keys. As I understand

A key of a relational schema = 
The minimal subset of a superkey that is still a key = 
A candidate key


Is this correct or not?
Just found out very neat explanation:

superkey: a set of attributes which will uniquely identify each tuple in a relation

candidate key: a minimal superkey

primary key: a chosen candidate key

secondary key: all the rest of candiate keys

prime attribute: an attribute that is a part of a candidate key (key column)

nonprime attribute: a nonkey column