Although traditionally the word podcast is associated with an audio file, many podcasts have shifted over to becoming video-based as well, typically this will allow them to interact live with viewers who are watching and then share the audio afterwards via a podcast feed.
This allows podcasters to reach a much wider market on many more devices.
You can make a podcast using your mobile phone & some free podcasting software, such as Anchor (which is owned by Spotify).
While the inbuilt microphone on your phone is usually good enough, you can buy microphones which plug into your mobile - this can be useful if you are interviewing people!
Watch the videos to learn more & click on the name of each tool to open its home page.
A suggested next step would be to listen to some podcasts and see what styles and features you like and then use the tools above to make a test episode of your own!
Good luck!