About add-ins
Add-ins are supplemental programs that extend the capabilities of Microsoft PowerPoint by adding custom commands and specialized features. You can obtain add-ins from the Microsoft Office Web site or third-party vendors, or you can write your own custom add-in programs by using Visual Basic for Applications. PowerPoint add-ins have the file name extension .ppa.
To conserve memory and increase the speed of PowerPoint, it's a good idea to unload add-in programs you don't use often. When you unload an add-in, its features and commands are removed from PowerPoint, but the add-in file itself remains on your computer for easy reloading.
Developers can use Component Object Model (COM) add-ins, which provide additional functionality in a variety of programming languages, including Visual Basic, Visual C++, and Visual J++. As a developer, you'll find information about designing COM add-ins in Microsoft Visual Basic Help. While you are developing and testing, you can load or unload a COM add-in in PowerPoint before you have a working installation program for your add-in.