[pmw]

It's an networking term to distinguish between ISP-owned and customer-owned equipment. https://en.wikipedia.org/wiki/Customer-premises_equipment

[jdsnape]

minor nitpick, but it's not ownership so much as location. Sometimes the ISP will own the equipment, but it will be located on the customer premises rather than the ISP premises. It's an important distinction as you can't just rock up and do stuff to it.