The topic of this paper is bias, but due to its connection with behavioral economics, at the very beginning it's going to be described what is behavioral economics, history, definitions, examples and applications of behavioral economics. Next, it will be stated what are the differences between traditional economics and behavioral economics through the views of different authors on the differences themselves. Also, in the chapter after the differences between traditional economics and behavioral economics, due to the presence and importance of bias in behavioral finance and heuristics, it' s going to be defined what is behavioral finance, what is traditional financial theory, and what is behavioral finance theory. In the same chapter, will be defined heuristics, what are the advantages and disadvantages of using heuristics, the advantages and disadvantages of the heuristics themselves, and what types of heuristics exist. The last chapter of the paper is reserved for the topic of the paper - bias. In that chapter, bias will be defined, what are the types of bias, the role of bias in decision-making and what are examples of cognitive bias. Also are mentioned two studies whose main task is to explain the application of bias in reality, how it is used and what is affected by certain types of bias.