Copilot is the brand under which Microsoft groups its AI assistants. It includes a general assistant for the web and Windows, Microsoft 365 Copilot for work in Word, Excel, Outlook or Teams, and Copilot Studio for building custom agents; GitHub Copilot supports programming. The assistants are based on large language models and, depending on the variant, can access organisational data in Microsoft 365 (as of October 2026).
ChatGPT is an AI assistant from the US company OpenAI, released in November 2022, which brought generative AI to a broad audience. It is based on large language models from the GPT series and answers questions, writes and edits texts, summarises documents and helps with programming. ChatGPT is available in the browser and as an app, in free and paid tiers as well as versions for teams and enterprises.
OpenAI is an AI company based in San Francisco, founded in 2015 as a non-profit organisation. Since its restructuring in October 2025, it has consisted of the non-profit OpenAI Foundation, which controls the for-profit OpenAI Group PBC (as of October 2026). OpenAI is best known for ChatGPT and the GPT language models, as well as the DALL·E image generator and the Whisper speech recognition model. Its models are offered through apps and an API.
A large language model (LLM) is a neural network trained on very large amounts of text, enabling it to understand and generate language. It works by calculating the most likely next token, step by step. LLMs write, summarise, translate, answer questions and generate code; well-known examples include Claude, GPT, Gemini and Llama. Without access to current sources, they only know what was in their training data.
An intelligent agent is a system that perceives its environment, processes information and chooses actions on its own in order to reach a goal. Today the term usually refers to software built on large language models that follows instructions, draws on knowledge and calls tools such as a search function or an API. How much an agent may do independently should be decided deliberately. Example: an agent answers customer questions using the product documentation.
