Insurance underwriters assess the risks associated with insuring people and assets and price the risk.
Investment banking underwriters guarantee a minimum share price for a company planning an IPO (initial public offering).
Underwriters of commercial banks assess the risk of lending to individuals or lenders and charge interest to cover the cost of taking on that risk.
Insurance companies assume the risk of a future event and collect insurance premiums in exchange for a promise to reimburse the client in the event of damage or its occurrence.