Audio File Formats Used For Podcasts

When I download podcasts, they'll, of course, be in a certain format. The three formats that I've come across of, are MP3, WAV (waveform), and MP4. My favorite format would have to be MP3 because it's the smallest file of them, and downloads fast. The WAV file was created by Microsoft and IBM. It's meant for storing bigger files, but the format is huge, so it takes forever to download a file if it's WAV. Last of all is MP4, which I think is pretty nifty because you can hold audio, photos, and videos with it, which WAV and MP3 can't do. A few times I've had to use this one, but the one I most have to use is WAV. It would be nice if I could download more MP3s, but that's just how the podcast episodes get sent to me.