About Audio and movie recording in QuickTime Player
You can make a movie using QuickTime Player and the camera in your Mac by clicking the File menu and choosing New Movie Recording. When the recording interface appears, the FaceTime or iSight camera becomes active (a green light appears by your Mac's built-in camera). Simply press the circular record button once to start or stop your recording.
Clicking the triangle icon gives you additional options, such as letting you choose whether to use the built-in iSight camera an external camera you've connected to your Mac, and lets you adjust the finished quality of your recording.
To make an audio-only recording, simply choose New Audio Recording from the File menu. Press the circular record button once to start or stop your recording. You will notice that the current running file size is displayed on the bottom right of the controls while you're recording; this changes to the total elapsed time when you stop recording. The sound meter (located at the bottom of the controls) makes it easy to ensure your volume level is consistent, and is helpful for making sure you're sitting an appropriate distance from the microphone. About 21 inches of distance between you and the microphone is a good place to start.
Clicking the triangle gives you additional options, such as letting you choose whether to use the built-in microphone on your Mac, an external microphone you've connected to your Mac, a microphone from a connected Apple display, and lets you adjust the finished quality of your recording.
Tip: Changing the quality from High to Maximum will produce a very high-quality uncompressed movie file. However, uncompressed audio files can use large amounts of disk space.