What does the broker or the insurer mean?

Nobody knows what that means. That's a gibberish statement. There are brokers (and agents) who sell insurance for insurance companies.

You see advertisements for the insurers (for the most part). Some big ones are GEICO, Progressive, American Family. These are the companies that develop and sell insurance policies.

Brokers (including agents) are the people in your local cities that  sell you the policies on behalf of the insurance companies. They receive a commission for their work (anything from 5% to 35%). The brokers/agents will be able to figure out  what your individual coverage needs are and help you get the right coverage.

Broker is an insurance agent that sells you the policy.      The insurance company pays any claims.

An insurer is an insurance company and has to pay claims if the time comes.  A broker is essentially a sales person who helps set up or negotiate the deal but doesn't pay claims.

A broker deals with many insurance companies. As compared to you buying direct from the underwriter.