At par, or the par value of a bond, is the price the issuer pays for the bond when it is issued. It is the face amount listed on the bond and the amount of money that the bond will be worth when it matures. After the bond is issued, the price of the bond may increase or decrease due to prevailing interest rates, time to maturity, and credit ratings. The par value acts as a reference point when it comes to assessing the performance of a bond and the yield that it pays. If a bond sells at par, then the investor will be paid the face value of the bond on the maturity date. Bonds that are trading above par are said to be trading at a premium while bonds that are trading below par prices are said to be at a discount.

Conversely, if a bond is trading at a discount, then the investor will receive less than the face value of the bond when it matures. To compensate for this, the bond will offer a higher yield. Similarly, a bond that is trading at a premium will offer a lower yield as the investor has already paid more for the security at the time of purchase.

At par is an important concept for understanding the performance of a bond over time. A bond trading at or near its par value indicates that the bond is performing according to expectations and that the underlying fundamentals remain unchanged. Changes in par value can provide investors with an indication of how the market as a whole views the security. If a bond is trading above or below par it can also provide an indication of underlying changes in the issuer's balance sheet.

At par is an important concept when it comes to understanding the performance of a bond. Par value provides investors with a reference point for assessing the bond's performance and yield that it offers. It is also a key factor in determining what price investors will receive when the bond matures. Changes in the par value of a bond can also provide investors with a good indication of how the underlying conditions of the issuer have changed. By understanding how at par works, investors can better assess the performance of a bond and the yield they will receive at maturity.