“Occurrence” or “Claims Made” refers to the type of coverage you’d be purchasing. This affects when you are able to report a claim on your policy.
Claims Made: You are only able to report a claim on a claims made policy while the policy is active. For instance, if you let your policy expire, and then six months later a former patient brings a lawsuit against you for an incident which occurred during the policy period, a claims made policy would no longer cover that claim (unless you purchased an Extended Reporting Endorsement, or “Tail Coverage“).
Occurrence: An occurrence policy covers you indefinitely for incidents that occur within the policy period, meaning you are covered for the time period during which you had the policy even if it is no longer active. It is essentially the same as a claims made policy with a built-in Tail.