What is Insurable interest?

The policyholder's real financial interest in the preservation of the property or person being insured: if the property is lost or damaged, the policyholder personally suffers a financial loss. This principle keeps insurance from turning into a gamble: one cannot take out insurance "betting" on someone else's house burning down. The interest may arise not only from ownership but also from a lease, pledge or debt relationship.

Source: Britannica: insurable interest