AddIn (Add-In or Add In) is a synonym for plugin - a program that is triggered by a host program allowing third party developers to manipulate or extend the hosting program.
Add-In (AddIn or Add In) is a synonym for plugin - a program that is triggered by a host program allowing third party developers to manipulate or extend the hosting program.
Typically, whether these programs are called "addins" or "plugins" depends on the programming language and platform. For example, in wordpress they are called plugins whereas in ms-office they are called addins. Some programs also call them "addons". In any case, these programs add or extend functionality to an existing program.
In most cases the hosting program will expose an extensibility interface to the hosted code, allowing it to execute tasks.
The most used types of Add-Ins are those automating the Microsoft Office programs (Word, Excel, Powerpoint, Outlook), browsers (Internet Explorer), IDEs - Visual Studio. But other non-Microsoft programs provide COM Extensibility as well (Skype, Altova software products, Photoshop, AutoCAD and many others).
In most cases the Add-Ins use COM object interfaces (that allow the Add-In code, if started from a standalone executable to instantiate the host program and then manipulate it) exposed by the hosting software.
