This is a simplified explanation of what frames are. If you want to make movie soundtracks, then this is just an introduction to a key concept, and you will want to learn more.

Frames values are for positioning splits exactly at video and audio frame borders. Check the “Snap To” box in the Selection toolbar, set your time value to the appropriate frame type, and then when you make splits or cuts, they will exactly match the frames. Any audio outside of the frame borders will be lost and possibly create a click.

National Television System Committee (NTSC) frames pertain to analog broadcast television in North America, some South American countries, and a few other countries. The NTSC drop frame rate is 29.97 frames per second (fps), and the NTSC nondrop frame rate is 30 fps. Audacity supports both. Why two? Why the odd 29.97 number? This is an old standard dating from the black-and-white TV era. The black-and-white broadcast frame rate was true 30 fps, but when color was added to the broadcast signal, the frame rate, for various technical reasons, was slowed down to 29.97 fps. Now pay close attention, because I am going to call on all of my mighty explaining powers to explain the difference ....