Surprise hit Serial, with 1.2 million listeners per episode, has everyone talking about how podcasts are the new hot thing, despite having been around for 10 years (and radio dramas since the 1920s). In fact, podcasts apparently confuse so many people that Ira Glass got his 85-year-old neighbor Mary to explain how to listen to one in a video you can see here. Here’s Slate’s list of the best 25 podcasts ever, with Serial ranking at #4.