Couldn't find a similar topic elsewhere in these forums, so for newbies in general:
- Half and Double ropes are synonymous
- Twin ropes are different.
Without wanting to re-invent the wheel (i.e. I'm lazy), check out http://www.tradgirl.com/climbing_faq/ad ... tm#doubles.
If you don't know the difference, you should probably stay safe and buy a single rope.
Anyone want to add more?