Question about time machine.

Hello,
If i set up time machine to backup to an external hard drive, will i be able to look through what it backs up and grab files or update files manually if i need it? Say i update my resume or update my music can i just drag that into the time machine backup... or how's the time machien backup work... is it a file i can't ever change?

TM is automatic backup. no need to drag files to it. they will all be there if you pick the drive to backup. internal or external does not matter. it will NOT backup an FAT formated drive. just have a large enough dedicated TM drive to have it capture enough history. i have a 2TB drive set up with raid 0 (mirrored 1TD drives) once its full the old backups are erased and new ones are added. i have 4 external drives and of course the internal drive backing up to the TM unit.

I'd like to add a TM question:

When I look through my backup files via TM and try to open a Text Edit file, it works fine. But when I try an OpenOffice file (.ods extension) it only gives me this "preview" window
It won't open the file so I can view the contents.

Why is that?