The closing methods define how the write process is finished. Depending on this method you can write more data to the disc or not.
This method only finishes the writing of the track. The session and the CD/DVD stay open and you can write additional tracks to the existing session. Please note that normal CD-ROMs or Audio CD Players are not able to use these CDs until they are finished.
If the session is closed, every normal drive is able to read the disc. Of course the medium itself must be readable. Not all CD-ROM drives can read CD-RW CDs. Please note that a normal CD player is not capable of multi session and will only detect the first session on your CD. Make sure that if you write Audio CDs, they are always in one session. Please note that any tracks that you add will be in following sessions.
This option is a kind of write protection to the disc. If you select this option, no one can change the content of the disc, however a CD-RW can still be erased.