Historical Data.
Trends are relevant historical bookings which are similar to the journey in context. They give a sense of current ticket booking and cancellation scenarios for that train and are important for curious users. The trends show four most important factors that determine the chances of confirmation of a ticket, namely the initial status (waiting number on the date of journey without considering any cancellations), the final status just before the journey, the number of days between booking & journey date and the journey date itself. See
what do the Trainman trends mean?