Understand travel terms and travel agents speak!
Backtracking is when you start flying in one direction around the world, then turn around and travel back in another direction before continuing in your original direction.
Backtracking can be allowed on some RTW tickets but is not an efficient and cost effective way of travelling around the world. More on backtracking.
A code-share flight is when two airlines come to an agreement (or alliance) to provide tickets on each other's planes.
This means that you book a ticket with British Airways but end up flying on a Qantas plane.
You can typically see when you are travelling on a codeshare flight by the flight code on your ticket. 'BA1' would be flying on a British Airways plane whereas 'BA41234' would be a code-share flight on another airline's plane.
An online stop is a stopover to your final destination which is in a continuous direction to your main route.
Good carriers for online stops are Air New Zealand who have a variety of Pacific Island stops to choose from and also Emirates who offer some more off the beaten track online stops in Asia such as Male, Colombo and Karachi.
An open jaw is a surface sector at your final point of turnaround - or furthest point from where you started.
London - Singapore - Perth surface to Sydney - Los Angeles - London
Published fares are non-discounted tickets and are based on exchange rates so may fluctuate until final payment.
It is worth noting that some RTW tickets are in fact published fares. This means that they will be the same price wherever you buy them from as your travel agent can not change the fare.
You can often tell if your ticket is a published fare as it will be booked in either Y, J or F class but this is not a totally water tight guide. Your travel agent should warn you.
RTW (Round The World ticket). Most RTW's route via Australia or New Zealand and consist of on-line stops en-route. It is possible to purchase round the world tickets that do not go via OZ/NZ (Northern hemisphere round the world tickets) but these do tend to be a little more expensive.
A surface sector is when you travel independently between two flight points en-route to your final destination. For example:
London - Bangkok surface to Singapore - Sydney - Los Angeles - London
Touchdowns can occur on direct flights!
This means that your plane will land but will only land for re-fuel or to let passengers on and off. You will NOT have to change planes and it should not affect you at all.