How many Copilots are there? Fewer than you think

Why does Copilot in Microsoft 365, for example, also use data that is integrated into the M365 search via a connector, but Copilot in Word does not? Or to be more general: What is the difference between Copilot in Word and Copilot for Microsoft 365? Let's just ask him ourselves.
Prompt in Copilot in Word: What makes you different from Copilot in Microsoft 365?

The prompt was used with the "Draft with Copilot" feature:

The detail "Copilot in Word is more suitable for users who need more specific and detailed suggestions and feedback on their writing" in the generated text makes the difference clear. It says that Copilot in Word is a writing assistant. The specification that Copilot should act as a writing assistant here is like telling a prompt in ChatGPT, that the AI should act as a travel guide and that the focus should be on suggestions for a weekend in Rome.

The technology behind this is called Retrieval Augmented Generation. In general, every prompt that a user enters is pre-processed by the Copilot Orchestration. This is where the Retrieval Augmented Generation architecture is used. Although this step is not mentioned by name in the architecture diagram, it is explained in this video by Mary Pasch, Principal Product Manager at Microsoft for Copilot: How Copilot for Microsoft 365 works: A deep dive.

A term that is also frequently used is "grounding". In the end, it means the same, i.e. adapting the prompt entered by the user, respecting the context of the used app an combine these factors to achieve the best possible result. Details on this are shown in this overview:

Source and further details can be found in this article from Microsoft: Microsoft Copilot for Microsoft 365 overview.

Retrieval Augmented Generation (RAG)

Depending on the app from which the prompt is sent, the Retrieval Augmented Generation technology decides which information sources are used to generate an answer with the help of the LLM. This aspect, called Information Retrieval System, can also be used with Azure AI Search. The article Retrieval Augmented Generation (RAG) in Azure AI Search describes how the technology works, which is also used by Copilot Orchestration.

How Copilot for Microsoft 365 decides which plug-in to use

There is also a similar effect when using plug-ins. How does Copilot decide which Plug-Ins to use to respond to a prompt? This also happens in the Copilot orchestration. The article How Copilot for Microsoft 365 decides which plugin to use describes what should be done when creating Plug-Ins so that Copilot Orchestration can evaluate them properly. The app description is located in the app manifest:

Roundup

Although this does not answer the initial question of how many Copilots are there. But it is now clear that there are far fewer than you might think. Copilot in Microsoft 365, Copilot in Word, Copilot in Outlook etc. are all the same engine, which is only used differently through orchestration and pre- and post-processing. Solutions such as Copilot in GitHub etc., however, are independent solutions.