TechTool Deluxe is a program that is distributed by Apple and was created by Micromat. It is basically an all-in-one utility that allows you to scan your computer for errors. However, it is more than a utility that checks for disk errors and that type of stuff. It also, runs diagnostics on your hardware to make sure that your computer is running the way it should be. Items TechTool Deluxe scans for are: Processor, RAM, Video, USB, Drive Hardware, System Formatting, Directory Scan, Surface Scan, Random Read, Random Write, Linear Read, Linear Write, Seek, Read Buffer, Write Buffer, Volume Structure. In simpler terms, it scans your processor, memory, video card, usb ports, and hard drive capabilities to make sure that everything works correctly.
In terms of user-interface and simplicity this application is as easy as it gets. You open the program, check the boxes that you want to diagnose and hit scan.
The good thing about having a program like this is that instead of having to take your computer to an Apple Store if you suspect something is wrong with it, you can do a physical hardware scan yourself. Also, if something breaks on your computer, you may need to send it in to Apple for a direct fix. This will allow you to tell an AppleCare technician over the phone what you may think may be possibly wrong with it before you send.