computer operating system -- can be interpreted as: computer AND operating AND system "computer operating system" -- is usually interpreted as a phrase (the words adjacent to each other and in order, just as you input them) computer and "operating system" -- this will be interpreted as the phrase operating system with the word computer somewhere in the entry.
For any ending, use the wildcard * (asterisk), example: vehic* [vehicle, vehicles, vehicular]
AND, OR, NOT -- it's Boolean logic (Smile! see tip sheet)
Searching for images: This is a specialty search that most systems do not support, although some show thumbnails so you can tell if an image is included. Google Images and ScienceDirect's search of Elsevier scholarly journals are two resources. Flipping through books or encyclopedias in the library works, too!