Left and rightPlay the left and the right channel. You should hear each one only on its own side. If they are the wrong way round, the cable, the headphones or your system settings are reversed.
Stereo movementThe sound moves from left to right. It should travel smoothly, with no hole in the middle.
Frequency sweepA tone goes from low to high. The screen shows its frequency, so you can tell where you stop hearing it. That depends on your equipment and your hearing, not on this tool.
Phase testThe same bass tone plays in both channels. In phase it sounds full; out of phase it sounds thin and the bass seems to vanish. If the first one sounds thin, one speaker may be wired the wrong way round.
Many laptop and phone speakers cannot play below about 100 Hz, so you may hear nothing at 30 or 40 Hz: that is normal. This is a test for your equipment, not a hearing test or a medical test. If you hear distortion at a low volume, the speaker or the cable may have a problem.