Often in college, you will have to read critically for classes and this can be in a textbook or in a piece of literature but the point of reading these texts is to extract some sort of information from it. This is significantly different than reading casually or for pleasure in one's free time.
When reading for pleasure, these reading techniques are unlike those used when critically reading. In class, we discussed the various ways to critically read a piece of text. Some of these examples were taking notes, re-reading the text, as well as looking up definitions of words that one is unfamiliar with. When reading for pleasure a reader isn't as concerned with capturing the point of the text and is looking for entertainment, not the main takeaway.
Another difference between critical reading and casual reading is the actual texts you are reading. Often when we are critically reading a text, it is something challenging or out of one's comfort zone. For example, when casually reading you will pick a genre that is more to your liking or at your reading level, but when you are critically reading a text it is often difficult to find the meaning or theme so it becomes more difficult.
A difference between casual reading and critical reading is when critically reading you are searching for many things that you are not normally looking for. A critical reader has to be aware of themes, character developments, plot, authorial intention, and many other factors. When one is casually reading they will pay attention to these characteristics of texts but will not analyze them so thoroughly. It becomes less about what the reader wants to get out the text and more about what was intended by the author. It is important to critically examine the many different aspects of the text to get a more defined sense of the text.