Built-in Bluetooth Playback：You can connect external devices such as mobile phones, PC, Mac, etc.With mixer audio interface, support MP3 / U disk and other devices direct input, built-in MP3 ...

An audio mixer in this context, is a device that combines four or more inputs alongside a built-in audio interface, or stereo ...

You don't have to spend a lot of money on one if you aren't concerned with high quality. However, the better the quality, the more professional your audio sounds. No one will listen to your podcasts ...