This is overkill in most situations, and file compatibility is limited. The Maximum quality setting saves AIFC files using PCM S24 codec and produces rather large files.
This is good balance of quality, file size and file compatibility. The High quality setting records M4A files with variable bitrate using the AAC code. Newer Macs have only the Microphone available as the audio source. Older Macs will generally have two input sources: Build-in Microphone and a Line-in from the 3.5mm jack.