As with so many things in the audio world, there are lots of important concepts that are mired in complex terminology that make it hard to grasp if you are not an electrical engineer or do not possess an advanced degree in acoustics and/or physics and pure math.
Just for a really simple oversimplification - if 2 wave forms go up and down and the same time, and you can sort of superimpose one on tope of the other, they are IN phase. If you then shift one of them in time (left or right) just a little bit, they are no longer in phase.
Frequency is how often a wave form goes up and down (1 up and 1 down is 1 cycle) in a second. 1 cycle-per-second is called a Hertz (Hz).
And amplitude is how high (or low) the up (or down) part of the wave form is.
In the article I just read, the author talks about the important relationships between phase, frequency, and amplitude. And of course these things mean very little unless you also throw in another variable - time.
Yeah, if I didn't know better I'd think I was having one of those nightmares where you're back in school studying for a physics class test on wave mechanics. You remember your wave mechanics, right? The terms phase, frequency and amplitude were the staple concepts in those chapters. Well, guess what? It turns out that chapter was going to have real-world application to your foray into audio recording. Exciting right?
Read more about these things and how they relate to your audio at the following article.