When you buy an insurance policy, the price you pay is known as the premium.
You’ll usually pay premiums in advance, to cover the whole duration of your policy term. That term is normally one year. Most providers (like Square One) offer monthly payment options, but you might also choose to pay for the full term up front.
When you pay in advance, the insurance provider hasn’t actually earned all of that money until the year has passed. Since you’re exchanging the money for a year of insurance coverage, the insurer must provide that year of coverage before they’ve earned the premiums—that’s when we call it earned premium.