Despite of multi touch fever around the world, resistive touch screens are still popular due to its reliability, low-cost, and easy-to-use. The following links and resources will help you find ways to understand resistive touch screens.
Illustrations: One picture is worth a thousand words.
Touchscreen Technology Explained, touchscreen Specification and Touch-screen Application Areas covers four, five, eight wire, and digital matrix technologies.
Compare All Resistive Touch Technologies adds six and seven wires as well as four, five, and eight wires.
... and one animation is worth a thousand pictures.
How AccuTouch Technology Works
Using resistive touch screens for human/machine interface is a nice tutorial to understand four and five wire touch screens. It gives the configuration, equivalent circuits, and data processing process of resistive touch screens.
Application Note [AN-004]: Resistive Touch Panel Technologies explains the structure, configuration, and circuits of 4-wire touch panels.
The Technology - 4-Wire Panels - How They Work contains very good illustrative figures to understand operating principles of 4-wire resistive touch screens.
Touch Screen Control and Calibration - Four-Wire, Resistive describes many practical math equations and circuits of four-wire touchscreen panels.
How a Five-Wire Touchscreen Works details 5-wire touch screens.
How To Calibrate Touch Screens lets you know how the calibration of resistive-type touchscreens is done. I also recommend Figure 1 and Figure 2 that nicely conceptualize the structure and the equivalent circuit of resistive touch screens.
Palm rejection on resistive touchscreens is essential for table PC applications. For those applications, palm rejection is important because your palm naturally touches the screen during pen writing.
Circular polarizers in resistive touch screens deals with the outdoor viewability of resistive touch screens