Since you are going to the United States for work, you need to apply for an Overseas Employment Certificate (OEC). Every OFW is required to get the OEC as this is a requirement under the rules and regulations of the Philippine Overseas Employment Administration (POEA).
Its purpose is to ensure that Overseas Filipino Workers (OFW) are documented and protected. There are several requirements before you can get the OEC such as the contract. Ideally, this requirement will protect Filipinos from being duped by illegal recruiters.
We can consider the OEC as our exit pass. If you have an OEC, you will not pay the travel tax (which is about P1,620) and the terminal fee (which is PhP 750).