# What is difference between r, and r(R) in DBMS?

Sorry, for asking such a basic question.

I am really confused between small 'r' and 'r(R)' being interchangeably denoted as 'relation' or 'relational instance'. I know, that R is a relational schema.

But, can you please clarify for me difference between r, & r(R). Also, relation and relational instance can be used interchangeably?