In psychology, ‘bias’ refers to predictable errors in perception. Here’s a simplified explanation of how bias works.
To start, everything we experience ‘beyond our skin’ is initially registered via our senses. After we sense something we begin to process it using our central nervous system, or brain (roughly speaking). This second process, resulting from the reception of the sensing process, is generally referred to as perception.
Once we perceive the input from our senses, a lot of “stuff” happens. Some of it is fully aware to us (i.e., conscious), some of it is not (i.e., unconscious). Whether conscious or unconscious, our brains actively interpret our (tasted, heard, seen, etc.) environment.
The interesting truth is: We don’t always interpret the “objective” world accurately. (We can know this because two people can perceive the same stimulus in different ways. If their is a ‘Truth”, both can’t be right; right?)