For a while, getting into modern Doctor Who was easy. The long-running BBC show is broken up into two distinct eras: The “Classic Era,” which ran from 1963 to 1989 (followed by a mid-’90s TV movie) and the “Modern Era” (or “NuWho” as it’s sometimes called), which kicked off in 2005 with a soft reboot and is still ongoing. Since the revived show was explicitly designed with new viewers in mind, anyone curious about the series could simply start with season one and go from there, while relying on any number of guides (including The A.V. Club’s) to explain the far more convoluted Classic Series. But things have changed since then. NuWho will soon have been on the air for 13 years, 11 seasons, and five central Doctors. It’s now an intimidating beast in and of itself. For those who want to get a better grasp on modern Doctor Who before tuning in to watch the first female Doctor make her debut, here’s everything you need to know.