"Open jaw" means a round-trip ticket where you fly in to one, then out of a different city. For example, I fly from Seattle/Paris, but then come home Rome/Seattle. It's all booked on one ticket. Open jaws often are the same or not all that much more expensive than a RT into and out of the same city, so can be a very good value/idea depending your itinerary.

Purchase two separate one way-tickets would usually be a LOT more expensive.

Just to add to Suze's comments. We often fly open jaw. Not only is it usually not more expensive but it keeps you from backtracking to your original city which can save a lot of time and can add as much as day for sightseeing etc. If you're checking fares, most web sites will let you chosse "multi city options" so you can plug in your arrival city and different departure city.

And yes, separate one-way tickets are definitely not the same thing and can often be VERY expensive in comparison.

Thank you both, I figured I was doing something wrong as the one way tickets didn't seem like a good deal at all. Dfr, can you tell me what website you use? I usually use air fare watchdog or fly.com but can't find the multi city option on either one of them. I'm not sure if it matters but we are looking into flying to Thailand and home from Cambodia, or the other way around, whichever ends up being cheaper. Thanks again.