Chatbots are a famous answering and text generation tool which became more popular with its real time based answering mechanism; use of Artificial Intelligence (AI) made them widely acceptable. Older version of Open AI's ChatGPT has issues like limited memory, inconsistent responses, and limited domain knowledge compared to ChatGPT- 4. ChatGPT-4 is able to answer like human in real time; it can write essays, poems, generate stories too. At present ChatGPT from OpenAI seems to be leading the trend compared to Bard AI, Bing AI, ChatSonic, OpenAI playground, LaMDA, Socratic, etc. This paper gives a brief knowledge on how ChatGPT got trained, its internal working mechanism, guidelines for effective utilization of ChatGPT and future of such AI based text generation tools.