Investment banks connect buyers and sellers in different markets. For this service, they charge a commission for successful transactions. The trades range from megadeals to simple stock trades. Investment banks are designed to finance or facilitate trade and investment on a large scale. But that is a simple look at how investment banks make money. There are a lot of things for what they really do. When operating effectively, these services make the market laxer, reduce uncertainty and eliminate inefficiencies by flattening the spread.