An external hard drive gets its power from an AC-DC adaptor. A portable hard drive draws its power directly from the device its plugged into, via a usb connection, and requires no additional power source.

They work exactly the same way, so it's just a matter of preference which phrase you use. Go with the adjectives - if you're carrying it from place to place, you might decide "portable hard drive/disk" is a better description. But if it's permanently plugged into your computer and doesn't move, then you might have doubts about calling it "portable". :)

Both drives are the same thing, the smaller size is easier to carry, so it is called portable drive and the bigger one is called external drive. Both drives requied external power and data cable, it can be SATA or USB. the data transfer, SATA is much faster than USB.

They are the same thing....just different ways of saying it.

They do the same, the difference is that the portable are way smaller than the others =)