How to find previously played episodes in the Apple Podcast App
While every podcast app has its own way of displaying the episodes, all should have a way to listen to previous ones. For the Apple podcast app, which is found on your iPhone and iPad, it tends by default to only show you unplayed episodes. But you can see previous ones too.
Here's how:
While any episode is playing, look for 3 dots in the lower right corner (if you haven't played the episode yet, and see a list of episodes, the three dots will be on the right side of the screen).
Once you click on those three dots (also called the menu), select "Go to Show" from the menu that appears, and it will list all unplayed episodes. Scroll past all of these, and you'll see an option to select "Previously Played" episodes.
Similarly, if you HAVE listened to an episode and you don't want to listen to it again, click the 3 dots to the right of an episode, and select "Mark as Played."