Bonds are an investment to get a 'fixed income'. Bonds are a form of indebtedness, similar to a loan with interest. You pay a certain price for a bond (i.e. a loan, where you lend someone money), and then each year you receive a fixed payment in return (i.e. interest on the loan). Bonds are issued by governments or companies.
You can sell the bond for higher/lower than what you paid for it, depending on its worth. They are usually low risk than equities, meaning the payment returns are lower too.