To partially answer the question what is audio editing? - I will say that if you have no intention of ever dabbling in the exciting, inexpensive and fun world of audio recording (it really is much easier and cheaper than most people ever thought possible), then I guess you really don't have to care. Let other folks have the fun. But if you are one of the curious ones, or have already started recording and producing audio, then audio editing (and hence, sound editing software) is not just a good idea, it is absolutely and utterly essential...but still cool!
I don't care what the real definitions are of some of these terms I define in these articles. This is my definition. Audio editing is making changes to already-recorded audio on purpose. I'd bet THAT definition isn't written down anywhere else. Let's examine it. It's always a good idea to get the best quality sound at the source, with good space, adequate equipment and good technique. If you get THAT part perfect, there MAY not be any editing required. But in the real world, where I believe I am living, those instances are rare.
How about an example? Okay, let's say you are recording your voice for a podcast or audio book. After the recording, you play back the result and notice three things. Your "P" sounds were too loud, causing that sort of "splat" sound. Some parts of the reading are very soft, and others are quite loud. Someone coughed in the background while you were reading and you can hear it between words. What will you do? You can always start over and do the whole thing again. Before computers, that would have been pretty much our only choice. Or you could fix all three problems with some audio editing software.
So you open the audio in an editor, like Audacity (which is open source audio software). First you zero in on the first place where the letter "P" popped out too much. You highlight that bit of audio on the screen and reduce its volume. You might also want to lower just the low frequencies there with some equalization (EQ). You do that to all the P-pops.
Then you notice that there are three or four places where the audio looks like it spiked...was much louder than most of the audio in the reading, which was actually not quite as loud as you would have liked it. But you can't increase the volume of the entire passage because once those spikes are turned up a little, they will distort...very nasty.
So you zero in on the spikes and reduce their volume (they shrink in size on the screen) to where it is closer to the average. Now you can turn everything up quite a bit without any distortion. Finally, you zero in on where that guy coughed between your words, and you simply delete it. Now you have fixed all the little problems in a matter of seconds.
There are obviously many more possible editing actions in audio. But with these tools you can produce higher quality audio much faster than having to re-record a million times. There are lots of tutorials on the web that talk about editing techniques.
At Home Brew Audio you can learn recording and editing and all nature of wonderful home recording stuff from short enjoyable video tutorials. Regardless of how you go about it, audio editing is vital if you work with audio. Now get recording!