A customs broker is a professional who has vast knowledge and experience in customs laws, tariffs, rules and regulations.
The customs broker works to ensure the clearance of imported or exported goods or merchandise from authority, preparation of import or export documents including computation and payment of duties, taxes and other charges accruing thereon.
If you're importing or exporting goods overseas then you should hire a customs broker to take care of the customs clearing.
It can be a real headache to deal with customs if you're not sure what you're doing and I would rather let a professional customs broker deal with that job.