Start the Quick Time X Player and go to "File", "New Screen Recording". A small black window will popup. You can select the video quality, mic in, show mouse clicks and the place to save the video when you click on the arrow in the lower right corner.
To start recording press the red button. You can now choose to either capture the whole desktop or just a part of it.
Just click somewhere with the mouse or select the area to capture while holding the mouse button to start.
To stop just press the stop button and your video opens in the player window.
Pressing the arrow in the player bar will open a option menu where you can trim the video or share it on different plattforms like YouTube or Facebook.
Creating videos of your desktop applications and sharing them cant get much easier and its already built in your operating system. No need to purchase additional software.
This works with Mac OS X 10.6 (Snow Leopard) or higher.