Thread Priority: Change the thread priority of the encoder.

Bitrate: Ití»s a measure of the number of bits that it takes represent one second of sound. A higher bitrate means better sound quality.

Mode:
J-Stereo ¿C Joint Stereo Coding is a method to reproduce stereo sound at a high level of compression as realistic as possible.
Forced Stereo ¿CForce MS joint stereo on all frames.

Quality: Better output quality means larger file size.

On-the-fly encoding: CD tracks will be encoded directly into the desired format without temp file using this encoding method. Otherwise, the tracks will be extract into WAV files firstly.

VBR/CBR/ABR:
VBR - VBR stands for Variable Bitrate - as opposed to CBR.
CBR - CBR stands for Constant Bitrate.
ABR - ABR stands for Average Bitrate and is basically just one form of Variable Bitrate where the encoder tries to maintain specific average bitrate for the file so that the actual size of the resulting file could be estimated more easily.