I am burning an audio CD in Brasero, and so I've clicked Burn and a window comes up with one of the options asking if I want to "Burn the image directly without saving it to disc". What does this mean?
In order to burn an audio cd it has to convert to cdda audio format. It can do this on the fly or in advance, and save it to the hard disk, then burn to the cd. If the conversion is done on the fly, and the computer can't keep up, then you can end up with a ruined cd. This is generally not an issue on modern computers, so it is safe to burn the image directly without saving it to disc.