You will be a much more effective reader - and learn things more quickly and more efficiently - if you learn to identify KEY WORDS.

When you start to read a passage, you need to ask yourself -

Sometimes, this will be obvious from the title of the chapter or the paragraph headings.  Sometimes, your teacher may have set you a particular task.  Sometimes, you may need to read quickly through the passage to find out generally what it is about - and then read it again more slowly to pick out the keywords.

When you have identified the keywords, underline them or mark them with a highlighter pen.  It is a good idea to use several pens of different colours.  You might even develop a system that uses different colours for different types of information.