A bond is a contract between two companies.
Bonds have a maturity date. This means that at some point, the bond issuer has to pay back the money to the investors. They also have to pay the investors a little bit more than they paid for the bond.
Bonds are usually traded through brokers and are part of a financial instrument group called Fixed Income. Banks and financial institutions offer loans on different terms against the security of assets.
Simply put, a bond is a receipt given by a government or organization as an agreement to borrow money from another organization which will be returned at a later date with certain amount of interest or increment.