Im lost- beginner needs some help (or a lot)

Ok so ive heard of the arduino and would like to learn how all of it works. What brought me to this site those is that ive had a number of thefts at my home address and would like to set up a security system.
I would like movement activated security camera 2-3 cameras. I will be buying the cameras premade as I need a good resolution to make out faces/license plates/etc

I have tried looking at some beginner stuff and I am learning and will continue to though I need to get this done asap. Any help and advice is appreciated!

This link below is a camera that is basically what Im looking for though would like to be able to view a feed on my phone or computer internet
http://makezine.com/video/build-a-basic-ir-motion-sensing-camera-with-weekend-projects/

The Arduino has little to do in this project but read the sensor and trigger the cameras. It can have nothing to do with the video storage or analysis.

Sadly that page you linked is a little over simplistic and I think it raises unrealistic expectations.

though would like to be able to view a feed on my phone or computer internet

Maybe you would be better off using a Raspberry Pi for this project rather than an Arduino?