Who is a tester?

We know that everyone is perfect but not in all aspects. We usually do many mistakes in our regular duties. In the same way when a software is developed for a specific reason there could be many hidden mistakes. Out of them few may be silly mistakes but few are very big mistakes. If those mistakes are not caught in time those will leads to danger to the complete software product sometimes to the whole company. 

We known that no one intentionally do the wrong things but they may not aware that they are doing mistakes. Here when developing a software, a developer may not known that they are doing mistakes while developing a software. There can be any reason for that, developer may misinterpret the actual requirements or incorrect coding or sometimes inability in coding. To find out those mistakes someone need to go through the requirements and the actual development. In other words we can say that to cross verification is required to say that a software is correct. All these verification needs to be done by a good knowledge persons. In the real world every one is calling these good knowledge persons are TESTERs.