Evaluation is an assessment or appraisal of something to determine its value, worth, significance, and so on. It is used to determine the effectiveness, and efficiency of a thing. In organizations, evaluation is a very useful tool for assessment.
evaluation

It is used especially when there is an ongoing or completed project. A systematic and sometimes rigorous assessment of the usefulness, effectiveness, impact, and sustainability of projects are carried out.

Evaluation is of various sorts. It could be planning evaluation which is done before a project is started. There is the formative evaluation which goes on simultaneously with a project. Again, the summative evaluation which is carried out after a project is completed.

Evaluation is a very important exercise. Not only do organizations need it but also humans need to evaluate themselves in order to make some changes if necessary.

Princeton Hines