


For example, when you install Adobe’s Acrobat PDF reader, it installs an Outlook add-in that lets you make PDFs out of emails.

They’re intended to make it easier for you to use a product. You may never use the add-ins, or even be aware that they’re there, but they aren’t (usually) malware or anything nasty. However, most add-ins are installed automatically when you install a piece of software on your computer. You can install add-ins yourself by opening Outlook and clicking Home > Get Add-ins, which will show you some of the add-ins available to you. Add-ins are extra bits of functionality that software providers create to hook their application into Outlook.
