Teri,
I did some research on this too, but I haven't had one nor has my son, yet. So someone else could probably explain this better than I!
The Power Port is implanted UNDER the skin.They make an incision which is totally sewn up afterwards, so there's no visible device. (I watched a YouTube thing on it.) It's threaded into a vein but the membrane, kind of a rubber bubble, makes a lump under your skin. Then they poke the needle right through the skin, into the bubble, and voila into the vein. After use, it needs to be flushed to get all the medicine through and prevent clotting.
Seems like a good idea for small or deep veins.
Wishing you the best,
Sarah