Collective behavior is a generic term used across many different fields and context, and thus it can refer to very different kind of collective phenomena exhibited by animal and human collectives, such as collective locomotion, collective decision making or behavioral contagion processes. In this lecture, I will try to give a classification of different types of collective behaviors highlighting potential similarities and differences from a theoretical point of view. Further, I will provide a brief overview on how they are typically modeled. Finally, I will discuss ambiguities on what is actually meant e.g. by collective decision making, and how caution should be executed when adopting some idealized models from statistical physics to model real-world phenomena.