I have a basement bathroom with a tub/shower that I plan on tiling. My questions are- Is Duruck, Hardie board and wonderboard the same? The area behind the tub/shower will be unfinished/no drywall, etc. Do I need to have a water barrier either under of on top of the backer board?
You absolutely need to water proof the surround. You can likely use any product (durock, hardie, wonder) that is rated for wet use (not "green" board).
You will still need to fully apply a waterproofing to wet side of the backer. I strongly recommend using a physical membrane like kerdi, but plenty of people swear by paint-on treatments like redgard.
Your finished setup will be something like this:
shower air - tile sealant - tile - thinset - waterproofer - backer - studs