What is a Descriptivist view?
A descriptivist is someone who believes that books about language should describe how language is really used, rather than giving rules to follow saying what is correct and not correct: He was a descriptivist and believed that a dictionary should reflect the actual contemporary state of the language. Compare this to the definition below.
What is a Prescriptivist view?
A prescriptivist believes that there are correct and wrong ways to use language and that books about language should give rules to follow, rather than describing how language is really used.
Now, obviously we live in an analogous world. We are human and susceptible to flaw and error. It is impossible for anyone to be 100% of one category or another. There is always some minor part of you that identifies with your opposite view. These views are interchangeable depending on the subject you're talking about, and often change how you feel. Most often, people gravitate toward descriptivism.