I don't understand what analyzing audio means, but when I ran auto-import on my music files, the program began to report that it was analyzing files one at a time. After 30 minutes it had only examined a small fraction of my library.
MC can use the data that it collects from analyzing audio in order to insure that it all plays back at the same volume. Once it's analyzed all of your audio files, you can turn on Volume Leveling in the DSP settings. There are other things you can do with that information, but volume leveling is usually the biggest one.
What does getting online metad data w/o allowing program to contribute mean? I don't want MC12 to make changes in file tags w/o understanding what it's doing.
MC won't automatically fetch data online for your files. It can retrieve track data from the online database, but only if you tell it to. There are some automatic lookups that can happen, though. Like when you put a CD in the drive, MC can lookup the track info for it. Also, upon import, MC can automatically fetch cover art.
5. Changed: It's possible to get online metadata without allowing the program to contribute corrections.
This just means that you can now retrieve online data without also having the automatic submission turned on. In a previous (beta) build, MC would automatically upload cover art when you changed it so that other people could use that to help them get cover art. Now you can turn off the automatic cover art submission.
6. Changed: Getting cover art and analyzing audio are enabled by default in auto-import options.
Pretty much what it says. On a fresh install of MC, these two options will be turned on by default.