see also skimming, technologising the word
There are many different reasons why you might read something, but essentially, reading involves skimming (reading to get the main idea of a text) or scanning (looking for specific information in details). This often happens in tandem---skimming the catalogue to see what the interest of the library is, and then scanning to see if a particular text has been included---and has relations to other modes of information retrieval, e.g. browsing/searching.
In 1977, while facing a skeptical audience in a Q & A session broadcast live on Australian television, Marshall McLuhan argued “the word read means to guess -- look it up in the big dictionary. Reading is an activity of rapid guessing because any word has so many meanings -- including the word reading -- that to select one in a context of other words requires very rapid guessing. That’s why a good reader tends to be a very quick decision-maker.”1 This is very true of human reading, where multiple interpretations lead to various equivalent understandings of a text, but false when applied to machine reading, which only operates with predefined ways of interpreting text.
Image: A quote from Marshall McLuhan during a live television broadcast, 1977