is resolution measure in pixels per square inch? So is 1920 by 1080 that many pixels in a certain area or is it the entire screen?
Resolution is the number of pixels that make up the picture on your t.v. or computer screen. 1920x1080 means that there are 1,920 individual colored points of light across your screen's width and 1,080 across its height for a total of 2,073,600 pixels. Each pixel is capable of changing color as needed to display images on your screen. The higher the screen's resolution, the clearer the images it can display.
PPI or DPI is the measure of pixels per square inch and is wholly different than resolution. You can have a 24" 1920x1080 screen and a 10" 1920x1080 screen. The number of pixels will be the same but obviously the PPI on the 10" screen will be much higher than that on the 24".