When comparing both debt and equity valution methods, I understand, mathematically, the equation that connects the present value(PV) of the bond to

When comparing both debt and equity valution methods, I understand, mathematically, the equation that connects the present value(PV) of the bond to its maturity value and to the interest rate, yet I don’t understand the entire meaning behind it. If someone could explain this to me that would be great. Also, who benefits more from rises in interest rates, the investors or the issuers? Thanks you.