If you think of online music as a replacement for music over radio, you can think of podcasts as a replacement for talk radio. The same basic benefits apply. Listen when and where you want.
Unlike music, podcasts have not only made shows more flexible in location and time, they have added an incredible variety of subjects. Not just current news, but pretty much any topic you might be interested in. I tend to stick with tech podcasts myself, but I also listen to a few other's like the Incomparable Radio Theater, Mission Log, and the TED Radio Hour.
Most of the time I prefer podcasts to music when I go for walks.
While there are video podcasts, the majority of them are audio; and this is what the majority of the better shows do. Unlike video, there is no Youtube equivalent to compete with.
As for ads, well you can't remove them. However, ads are not as out of control in podcasts as they are elsewhere. They usually consist of a couple sponsor spots, where the hosts inform you about some service or company, often they have personal experience with the products. If you're really bored most podcast apps will let you skip forward by 15 to 30 seconds.
My favorite podcast app is Overcast. But there are many others.
As you might guess, I'm a podcast enthusiast.