Interest Rate vs. Borrowing Rate - Difference
The Interest Rate is a more general term, and can cover all shorts of financial transactions where one expects by a contractual clause to get their money back plus "a little something" (I am not referring to the expected profit from an investment, where the "little something" is not a contractual obligation).

So you can talk about "the interest rate of a loan" but also of the "interest rate of a deposit in the bank".  

The Borrowing Rate specifically refers to the Interest Rate that the entity under consideration (a business, a public sector, or an individual) has to accept to pay as this extra little something if they want to borrow funds.

So the "borrowing rate" is an "interest rate" - one among many kinds of interest rates.