Insurance companies earn money in two ways.
Underwriting is the process through which insurance companies select what risks to insure and decide how much insurance premium to charge for insuring those risks
Through carefully investing the received insurance premiums in high return investments they will be able to earn money on the invested insurance premiums
The most difficult aspect of the insurance business is the underwriting of polices. Based on a wide set of available data, insurance companies predict the likelihood that a claim will be made against their insurance polices. Insurance companies price products according to the likelihood of claims.
At the end of the insurance, the amount of insurance premium collected minus the amount paid out in claims is the insurance companies underwriting profit.
Insurance companies currently make the most money from their auto insurance line of business. Generally better statistics are available on auto insurance claims and underwriting on this line of business has benefited greatly from advances in computing technology.