It is designed as a parametric/graphic equalizer with a modular GUI which features an unlimited number of filters, multi-channel use, an extremely low latency that ensures its use with multiple interactive applications - an all around EQ app.
Equalizer APO does require a reboot after install but then it is good to go. You can slide the adjustments on the graphic EQ that is located in the top portion while viewing the analyses panel down below for the effects of the changes made. It also features preamplification/gain as well as balance modifiers.
Equalizer APO does require a sound card driver that supports APOs (this includes most onboard sound drivers), and you can not use APIs like ASIO or WASAPI exclusive mode.
It specifies Windows Vista or later but appears that it has only been tested on Windows 7, 8, 8.1 and 10.