Bonds are debt instruments that profit off of over time. When you buy a bond you are essentially loaning money to another party. There are many types of bonds with varying durations, interest rates, risk levels, and stipulations. They are typically slow moving vehicles but generally seen as "safer" investments than stocks. Investors often flock to bonds as a in times of increased volatility, however that is not a rule set in stone.
One benefit to a bond investment is that if a company in debt was forced out of business, anything left would be used to pay back the bond holders first, before paying the The downside is that the profit potential may be much lower than that of a stock investment.