The lower portion of the main player screen can show four different things:
You can switch between the displays by swiping up or down on the bottom half of the left edge of the player screen. There are three small, faint horizontal bars to identify the area.
The round set of skip buttons allow you to move forward or backward by fixed increments, in either seconds or minutes. Skip buttons (versus sliders or scrubbers) allow you to navigate within long audio without losing your context. For example, if you skip ahead too far, just skip back, and skip ahead again with a smaller increment. By default, the skip increment is in seconds, but tapping the clock symbol in the center of the dial switches from skip-by-seconds to skip-by-minutes. Skip-by-Minutes is indicated by a red background and a red clock hand.
The skip button values can be changed in the Preferences area. You can change the seconds and minutes of each button. You can also change the sec/min label suffix (for example, to "s" and "m").
The Episode Selector display shows a listing of episodes available for the selected podcast. Simply tap on a episode title to play that episode.
"What do the little symbols mean that I see on the left of the Part Selector items?"
There can be one or two symbols on the left side. The upper symbol denotes the play status of the audio: a red circle means the podcast has not been played or marked as seen, a blue and white pie shape shows how much of the audio has been played, and a black circle indicates the item was completed. The lower symbol denotes the download status of the audio file: A miniature download symbol (arrow pointing down) means the audio file is currently being downloaded, a paper/file symbol means the audio file is available to play.
Driving Mode provides an easier/safer way to pause or skip forward/backward while in the car. While in Driving Mode, tap on the cover image to play/pause, and swipe left or right to skip forward or backward. The default skip value is 30 seconds for both directions, but this can be configured in the Preferences area. By default, only the cover image on the lower half of the screen is used for Driving Mode controls, but there is a "Full Screen Controls" preference to make the entire screen active.
Swipe left or right in the upper title area to go to the next/previous part. You can also double-tap the title area to jump to the management listing of all parts/chapters/episodes. There, you can do things like view podcast information, download files, and delete files.
The quickest way to change podcasts is through the Shortcut Drawer. This can be opened using the button on the left side of the title area, shown with three small stacked squares.
The Shortcut Drawer keeps all your podcasts close at hand on the main player screen, sorted by more recently played. The artwork of each podcast is shown, simply tap on one to start playing that podcast wherever you last left it.
The Shortcut Drawer also provides an easy mechanism to check for new episodes of all your podcasts. Just pull down on the list and release. Podcasts with new episodes will be shown with a red dot with a white center.
Tap the Star button at the bottom of the screen to get to the speed adjustments. Tap on the rabbit to increase the playback rate, and the turtle to decrease it.
"What are the actual playback speeds?"
The values for the speed controls are: 0.6x, 0.7x, 0.8x, 0.9x, 0.95x, 1.0x, 1.1x, 1.25x, 1.5x, 1.75x, 2.0x.
The Sleep Timer must be enabled in the Preferences before first use.
You can also adjust the default settings for the sleep timer in the App Preferences.
To start/stop or adjust the Sleep Timer, swipe up or down on the lower left side of the main screen until you see the Sleep Timer controls (as shown below). Adjust the timer amount, or hit the Ep. End button to have the timer expire at the end of the current episode. Whe the sleep timer expires, it will stop the audio, and create bookmarks at the beginning and end of the sleep time period. You can add time to the sleep timer any time the sleep timer is operating, and up to a minute after it expires, by shaking the device.