Bond call price is the price at which a bond issuer is entitled to redeem, or “call,” its outstanding bonds before their stated maturity date, buying them back from whoever currently holds them. The specific call price, along with the earliest date the call right becomes available, is set out in the bond indenture at the time the bonds are originally issued, not negotiated later.
Why call prices are usually set above face value
A call price is commonly set at a small premium above the bond's face or par value, compensating bondholders for having their investment cut short before maturity, often when the issuer calls the bonds specifically because interest rates have fallen and refinancing at a lower rate has become attractive. This premium, sometimes called the call premium, typically shrinks the closer the bond gets to its actual maturity date, under a declining schedule written into the indenture.
Where the general concept is explained
Bond call price is a specific application of the broader call price concept, which also applies to callable preferred stock. See that entry for a fuller explanation of how call prices are structured, why issuers exercise call rights, and how the possibility of an early call affects the way investors value a callable security in the first place.