Here’s a great little video explaining how to use Phase Invert in Logic to deal with phase cancelling issues.
Phase cancellation is the result of two wave forms being out of synch with each other so that as one wave form hits a peak in its cycle the other hits a trough. If two waveforms are exactly out of sync in this way they can actually cancell each other out. More often, there won't be a full cancellation, but you'll notice a muffled flanged type of effect as they fight with eachother.
Phase cancelling can happen if you have two mics recording a single source. Because of the differences in time it takes for the sound to get to the mics, the sound can be out of phase and some parts of the two waveforms can actually cancel each other out. If you reverse the phase on one of the signals, then you can eliminate this problem.
Phase issues can often occur if you are layering percussive elements - like two kicks - in your track. The issue is worth understanding and is also fixable.
Most any DAW will have the option to flip the phase on a certain track - so just look out for it and be aware that it's worth testing when layering things to see if one way sounds better.