Listen to this Show If you are a new Mac user you may not know many of the ways to Quit applications on the Mac. There are multiple ways to do it... and I'll step you through a few.
Let's get to it:
Use the Menu Bar
Go to the Menu bar of the selected application and choose Quit. It's usually under the first menu, to the Right side of the Apple menu.
Use the Application Switcher to Quit
Hold down COMMAND and press the TAB Key. Continue to press tab to cycle throught the applications. Once you select the one you want to quit, press the Q Key. After it Quits, you can release the COMMAND Key and the application switcher will disappear.
Click & Hold
Click and Hold down the mouse button on the Application's ICON on your Dock. When you do the click and hold, after a couple of seconds a contextual menu will appear and from there you can choose QUIT. For those with a 2 button Mouse, you can alternatively RIGHT CLICK instead of clicking and holding. It also works if you hold down CONTROL and CLICK on the dock icon.
If you have an application that isn't responding at all, it may have frozen. So your solution to this is to FORCE QUIT the app. To do this one, you hold down the OPTION key and Click on the frozen app and choose 'FORCE QUIT from the menu. If that doesn't work, press COMMAND-OPTION-ESCAPE and it will bring up a list of running applications. Choose the one thats giving your trouble and you can choose FORCE QUIT from this menu. Force quitting does have some side effects... for example, any data that isn't saved in that App will be lost. However, if it's not responding anyway... you may have no other options.