To our knowledge, the English poet Alexander Pope was not a human factors researcher. But, he did hold a shared belief with the field when he said "to err is human". In human factors, we recognize that humans make errors; however, we do not believe that blaming the human is the solution. Instead, we want to research what causes errors and how to minimize the likelihood of errors occurring.
Oftentimes we preform tasks, especially typical ones, without any issue. Occasionally, we do make errors. Errors can be classified into two main categories:
Slips: Intending to perform an action, then accidentally performing a different action (right intent, wrong action)
The different action is often similar to the intended one
These errors are unconscious and typically caused by inattention
Mistakes: Occur when the users' goal is inappropriate for the problem/task at hand (wrong intent)
Conscious error that typically arises from a misunderstanding of the situation
Arise when we have incomplete/incorrect information about the task/system (mismatch of mental models)
A common method we use to analyze errors is to walk through where they might occur at each step in a task. This is called a task analysis (or hierarchical task analysis). Once the task analysis is completed, researchers can determine where the highest likelihoods of slips and mistakes are within the task(s) and then use this knowledge to address whatever research question they're trying to answer!
Norman, D. A. (1981). Categorization of action slips. Psychological review, 88(1), 1.