A siphon (or syphon) is a simple hose type device that you use to drain liquid from a container. The liquid in the container has to be higher than the place the liquid is going to drain to. A syphon is powered by gravity and vacuum - no electrical parts. It's very simple. It's not a brand name - it's a type of device. Some people use their garden hoses as syphons.
Python is the brand name of a hose like device that you can use to both drain water from your aquarium and put fresh water back in. It attaches to a faucet in a sink. When attached to a faucet, it is powered by a vacuum caused by the running water. Here's a link to their website:
http://www.pythonproducts.com/
You can buy Pythons at Petsmart or Petco or lots of other places.
I use a Python but I don't attach it to my sink. I use it like a syphon with a really long hose to drain my tank. when I refill my tank, I bring in a garden hose from outside if I'm replacing a lot of water. If it's just a few gallons, I use a bucket.
Lose the bucket - at least when you're emptying the old water!