Chatbots such as ELIZA and PARRY were early attempts at creating programs that could at least temporarily fool a real human being into thinking they were having a conversation with another person. PARRY's effectiveness was benchmarked in the early 1970s using a version of a Turing test; testers only made the correct identification of human vs. chatbot at a level consistent with making a random guess.
WeChat was created by Chinese holding company Tencent three years ago. The product was created by a special projects team within Tencent (who also owns the dominant desktop messaging software in China, QQ) under the mandate of creating a completely new mobile-first messaging experience for the Chinese market. In three short years, WeChat has exploded in popularity and has become the dominant mobile messaging platform in China, with approximately 700M monthly active users (MAUs).
ELIZA's key method of operation (copied by chatbot designers ever since) involves the recognition of clue words or phrases in the input, and the output of corresponding pre-prepared or pre-programmed responses that can move the conversation forward in an apparently meaningful way (e.g. by responding to any input that contains the word 'MOTHER' with 'TELL ME MORE ABOUT YOUR FAMILY'). Thus an illusion of understanding is generated, even though the processing involved has been merely superficial. ELIZA showed that such an illusion is surprisingly easy to generate, because human judges are so ready to give the benefit of the doubt when conversational responses are capable of being interpreted as "intelligent".