One problem with travel is there is just so much choice available. There are almost two hundred countries on our planet and visiting them all would take some doing, and a very understanding boss. Not only this but some of these countries are huge and somewhere like China or Russia is not a place you could see much of in a two week holiday. Another thing holding a lot of people back from travelling is the expense. Travelling the world costs money, but if you follow the example of the backpacker and are prepared to slum it a bit then you can do it relatively cheaply.
What most people end up doing is making a compromise; it is probably not essential that you visit places like Tuvalu or Kiribati, but even when you remove the smaller countries there are still a lot of places to visit. One way of getting around this is by doing a tour of different countries; you won't really see much of each country but you will get a taste of each and some great memories. A popular thing to do is by an around the world air ticket. This can be an open ticket and you could spend up to a year moving from one destination to another.
If you want to follow the example of the backpacker and travel the world on a shoestring then you will be staying in lots of hostels and only eating local food. If you are prepared to sacrifice luxury and don't party too much then you can make your money go a long way. There are some countries where it is claimed you can manage on a couple of dollars a day. Places like the islands in Thailand are a popular destination for