What is a primary appraisal?
Primary appraisal is the process by which a person interprets and assigns meaning to an event or potential stressor.
During primary appraisal of an event, a person evaluates how relevant the event is to her/him and what kind of impact it is likely to have. This results in a broader categorization of the event that influences the the way a person internally and externally reacts to the event.
For example, being snowed into your house could be appraised as good (if there is a snow-day and you were dreading school), bad (if you had plans with friends that you now have to cancel), or not relevant to you (if you are sick and weren't planning on leaving the house anyway).
Primary appraisal is part of the broader idea of cognitive appraisal proposed by Lazarus and Folkman, which characterizes the way people respond to stressors. For more detail, see: Folkman et al., 1986