The government is the largest issuer of debt

The government is the largest issuer of debt, issuing Treasury bills, notes and bonds.
Corporations also issue corporate bonds, which make up the second largest portion of the credit market.
Through corporate bonds, investors lend corporations money they can use to expand their business.
In return, the company pays the holder an interest fee and repays the principal at the end of the term.
When corporations, national governments and municipalities need to earn money, they issue bonds. Investors who buy the bonds essentially loan the issuers money. In turn, the issuers pay the investors interest on the bonds, and when the bonds mature, the investors sell them back to the issuers at face value.
Credit leads to an increase in spending, thus increasing income levels in the economy. This in turn leads to higher gross domestic product and thereby faster productivity growth. If credit is used to purchase productive resources, it helps in economic growth and adds to income.