Applications in Mac OS X are programs.  Mac OS X ships with several dozen of built-in Applications that allow you to do things such as create documents, chat with friends, store contact information, and modify the settings on your Mac.

Apple designed OS X to allow applications to be provided to OS X users as an application bundle (packaged unit) or packaged with an installer.

If you're familiar with Windows, you accustomed to uninstalling programs with the Add/Remove Programs option in the Control Panel.  With Mac OS X, uninstalls undertake a much different procedure.

An application icon is simply a representation for the entire application.  Tied to that icon are folders and files that essentially make up the application.  Let's demonstrate this with an example.

Each user has his or her own Library folder that contains files and settings specific to and individual's preferences, recent items, web site bookmarks, Address Book entries, keychain, and so on.

You can run multiple applications on a Mac, you're only restricted by your system's hardware and memory.  The more processing power and memory on your Mac will allow you to run more applications at any given time.