How do people become adventurers?

By adventurer I mean the people that I always seen on National Geographic and the newspapers or CNN. It’s those men and women that travel the world, and seems like they are living a real life journey or adventure. Something like Indiana Jones. Are there people who just travel to travel, and find an adventure on their way there? Or could they be professionals like archaeologists or humanitarians ? I’d like to go to another country and help out. I don’t care how long I will stay. It just seems like when I watch Nat Geo or the news, they always look like it’s something from out of a movie.