What is Clipping?
When a computer records audio data, there is a maximum volume at which it can properly capture audio. Audio that exceeds this maximum volume is not captured correctly, and is said to have clipped (in reference to the fact that the audio waveform of clipped audio looks like it has been clipped off, or flattened, at its maximum value). You can think of clipping as the audio equivalent of suddenly exposing your eyes to a bright light – because the light is brighter than your eyes can handle, you're unable to see anything but white.
Clipped audio sounds bad, and should be avoided.
How do I Avoid Clipping?
Your recording software will typically include a VU-meter, which indicates the volume level of the audio being captured. In Cast, this meter is shown around each partipant's photo at the right side of your Studio session. To avoid clipping, your VU-meter (and that of your participants) should never be filling up completely at any point when they speak.
While audio that is recorded too quietly is problematic, it's much easier to salvage audio that is recorded quietly after-the-fact, so erring on the side of a quieter recording is often wise.
Cast also keeps an eye on recordings and attempts to inform you in real-time when it first detects clipping.
What Can I Do if I Know I've Clipped?
Clipped audio is typically not salvageable. If you realize that you've just clipped while you're recording, your best bet is to lower your microphone volume, speak more quietly, or move further away from the microphone, and simply re-run the section you know to have clipped, and then cut that clipped section out after the fact when you're editing your podcast.