Raster (Computer Graphics class)

I just started working with Sketch book Pro and Photoshop in my computer graphics class and it's a whole lot of fun (Probably more fun once I actually start to know what I'm doing.)I am not very tech savvy, so when prof. Hopper, who teaches the class, goes on about pixels and dpi/ppi and what a raster is and what a vector is, at the time, I can only break all that info down into very simple, basic concepts before moving on to more. The media of computers is just so mind-blowing; the things to create on a computer and programs are just so vast,almost limitless, and elaborate(especially since they keep changing every- what? two or three years, maybe even one?. Anyhow, I've only been able to work with a few things so far while clicking buttons and finding out what does what, and came up with these.