Skimming is reading for gist, between the lines, in a semi-distracted state. A way to get the main idea of a text quickly, flipping pages, jumping pages with the spacebar, infinitely scrolling. I think of the pastime of skimming stones, as my eyes jump in [saccades](http://suncityvision.com/photos/info-eyemovements1.jpg) over the surface of the text.
Many folk prefer to read from paper than from a screen. A common complaint is that reading from a screen is tiring, especially when you just want the gist of a text. TL;DR. Sometimes this is precipitated by information about how long it will take to read an article or essay online.
Scanning is reading for particular details such as names and numbers by running one's eyes over every word in a line. Sometimes I find myself using a finger to guide my eyes when scanning a printed text. With a computer and full-text search capabilities, it's often as simple as pressing control- or command-F.
Scanning is also a process of photographing printed matter so that it may be digitally available for manipulation or electronic distribution. For this purpose, a [bookscanner](http://tenrec.builders/archivist-guide.html) is the tool of choice for many archivists. The bookscanner has two cameras, one to capture the odd pages, and one for the even pages. Most bookscanners consist of a system of pulleys which allow the book to be raised to two perpendicular sheets of glass, which will lay the pages flat and ensure the focus is correct. It's quite a workout, and is usually reserved for books which are difficult to find in digital format. Essentially the bookscanner takes two photos for each spread, and then these must go through a variety of processes to produce a digital book. Ultimately, the most useful digital books include a digital text layer generated by OCR (Optical Character Recognition), which allows you to control-F to find a word quickly with a full-text search.
