ChatGPT (Generative Pre-Trained Transformer) is large language model tool that uses artificial intelligence (or natural language processing), to answer user-generated prompts. It was developed by OpenAI and is available for public use. Some versions of ChatGPT are not connected to the Internet and query a massive dataset that was collected prior to 2021. Those versions cannot source answers to questions after that date.
Many tech companies, including Google and Microsoft, are developing internet browser extensions and platforms that point AI at the web. These capabilities are constantly (and quickly!) evolving. But in general, ChatGPT can only provide textual responses, unlike other bots or virtual assistants it does not reliably link out to the internet, show images or videos, or provide any non-textual media.
For a deep-dive into the inner workings, check out this blog post "What Is ChatGPT Doing … and Why Does It Work?" by Steven Wolfram.