What do people mean when they say “Brokerage”?

A brokerage buys stocks, bonds, funds, commodities on your behalf and holds them usually in a custodian account in your name.

They allow you to access markets that you can't usually access and charges you a fee for doing so.

You don't need a broker if you're buying local assets. Like, you can buy a 500K bond over the counter in a bank without a broker, or buy stocks from SGX by yourself.