Bonds are securities issued by government, municipality, financial institutions, companies, or supranational entities in exchange for a loan.
They prove the lender’s right towards the issuer for the return of the loan at a certain maturity. Also, the lender is entitled to collect a periodic interest – Bond Yield – also called the "coupon payments".
Unlike shares, bonds bring income for a limited period and the holder doesn’t have the right to vote in the deliberative bodies of the issuer. (Bonds are IOU - I owe you)
As a rule, bond prices (bond’s market price) and bond yields (the interest paid by the issuer) are inversely correlated.

A relevant indicator of the future interest rate changes is Government Bond Yields.
Government Bond Yields are financial instruments issued by the government which attest a public debt to the holder. They have a lower yield than other bonds but are more secure.

Government bonds have specific names:

If the bond’s price rises its yields decrease and vice versa.

The dynamics behind this evolution is as follows:
Bonds are safer investments in high risk aversion periods. A higher yield will attract more investors, creating more demand for the issuing country's currency. Thus, the issuing country's currency appreciates against yields. This is usually true for the fixed income securities.

We can use the Government bonds yield fluctuation in carry trade – trading a pair where one of the currencies belongs to a state that issues high yield bonds and the other belongs to a state that issues low yield. If the bonds yield differential is high, the stronger currency will appreciate even more.

Note: Carry trades works only for bonds which have the same maturity period.