ChatGPT uses Natural Language Processing. Its GPT model is called Generative Pre-trained Transformer. The key concept is ‘Pre-trained’. In computer science, in the past two or three years, the algorithms are being pre-trained. In language model, they look at a sequence of words and detect a pattern. They anticipate the set of words that could follow, and make sense. To learn these patterns, they use the data of Wikipedia and collection on the Internet. Thus they have pre-trained algorithms to generate new content based on these patterns. The word Generative in GPT comes from this. ChatGPT has learnt the patterns of human language, common word sequences, and patterns of word usage from data on the Internet.