There may be a lot of variation in how much you know about individual users. Some users may be pretty unknown, while you may have a lot of information about others. This user information could come from a long user history (i.e. a returning user), but it also could be supplied via an API, from a separate registration process, from contextual information like geolocation, and more. You may know a lot about a new user because the info is passed along, and you may know little about a returning user because the data isn’t saved! That said, having a user’s name, their preferences, their purchase history, their conversational style, and more can all affect how to open a conversation.