Pull up resistor simplified

[rainbow fox]

Hello there, I am still new to the electronics portion of robotics and I have come across a snag. I am very confused as to what a pull up resistor is and I would like a simple explanation that can help me to better understand this since this system is used in almost every micro controller. Thank you for your time.

[bdeuell]

Have you tried Google?
I wont be able to provide a better explanation than those already on the web which include pictures.

As you have said pull up/down resistors are very common. It took me a couple times to really understand them when I started in robotics.

If you understand Ohm's law draw a couple of circuit diagrams with a pull up resistor and switch in open and closed positions. Then work through the current paths to figure out the voltage potential at different points in the circuit. I think being able to explain it to yourself is the best way to truly understand it.