Video game companies need testers to identify software problems in games. Once the issues are identified, they are addressed by developer and the game is re-tested to make sure that the problems have been solved.
Positives to being a games tester: You get to play the newest games in their development phase. Also you're using a set of skills that many people only use in their leisure time.
Negatives to being a games tester: Sometimes the work can be repetitious as you may be required to play the same level of a game again and again to identify any areas of concern. Also even though you are doing the 'fun' part by playing the game, there is also a significant 'work' component in identifying and documenting errors, glitches or bugs.
Types of game testing jobs: In games testing there are a variety of different positions for many different skill levels. Some games testing jobs require only an ability to play video games. Other more senior level testing jobs may require years of experience in the industry. Games testing jobs are often a full time job, however 'beta testing' just before the full release of a game often requires hiring many temporary staff. Some testers use their initial gaming job as a starting point, later moving to other different roles in the industry, for example management, marketing, design or production.
As with any employment, if you really love your work you can gain a lot of job satisfaction and enjoyment, and can build a solid career.