It means middle man. Someone who acts as a trusted escrow or mediator.

Yes, using escrow is how it's done correctly. I suggest using a trusted escrow and observe the following advice carefully:

• Contact a trusted escrow directly. Ignore links and copy/paste messages or payment instructions either party claims to have received from the escrow.
• When contacting escrow, check and doublecheck the URL of the escrow's thread or profile page. Ascertain and ensure it's authentic and not spoofed or cloned.