A TEU is a measurement of shipment volume.

What is a TEU?

A TEU (twenty-foot equivalent unit) is a measure of volume in units of twenty-foot long containers. For example, large container ships are able to transport more than 18,000 TEU (a few can even carry more than 21,000 TEU). 

One 20-foot container equals one TEU. Two TEUs equal one FEU.