Equalization (or EQ) involves boosting or cutting certain audio frequencies in your song. Doing so can make certain parts of the audio field sound more bright or dull, and proper EQing is an important part of having a great sounding track.
eMastered's Equalization engine has 3 different areas: Low, Medium and High.
The "low range," refers to the lower frequencies / bass elements of your track, the "mid range," refers to the mid frequencies (often drums, guitars, pianos and vocals) and the "high range," refers to the top layer of your song.
Lowering a specific section will actually remove frequencies in that area while increasing it wlll boost those frequencies even higher.
For example, a song with a lower high range will likely sound darker and less bright than one with its range left at the center. This can be ideal for certain songs and styles, but other genres like EDM often desire very bright High Ranges.
We encourage you to tweak these settings to your heart's content to find the best one for your audio.