The most basic example of compound probability is flipping a coin twice. If the probability of getting heads is 50% (.50), then the chances of getting heads twice in a row would be (.50 X .50), or .25 (25%).
As it relates to insurance, underwriters may wish to know, for example, if both members of a married couple will reach the age of 75, given their independent probabilities. Or, the underwriter may want to know the odds that two major hurricanes hit a given geographical region within a certain time frame. The results of their math will determine how much to charge for insuring people or property.