Use alternate CD play routines: (Default: Disabled) Normally EAC will play (not extract of course) through the analog output of the CD-ROM and soundcard. When this option is enabled all CD play routines will work by extracting and digitally sending the audio data to the sound card. This has the advantage that no cable has to be installed between the drive and the soundcard. This is especially cool in Windows 2000 where other programs can also do this by setting this in Device Manager. Note that this feature is only recommended if you have a CD-ROM that is quite good in Digital Audio Extraction.

This option is for CD play only or for extraction too ?
Because it is not well explained in EAC and in the SatCP tutorial, or I don't get it.
Another question: Does EAC extract the audio digitally or analogue ?

It's only for playing the CD. Extraction is always digital.