If you need more information about what is going on inside Burn.app (e.g. what arguments are used to fire up a certain tool) you may have a look at the console window. This window throws out a lot of textual information such as the command lines for the tools, the backend tools' own outout, error messages etc.
You can open this window by selecting 'Tools'->'Console' from the menu.
The console uses different colours for different types of messages. 'Normal' messages are printed in black, error messages in red, and the backend tools' output in grey.

Blanking CD-RWs is necessary if you want to reuse a CD-RW or if you need to destroy its contents for any other reason.
Currently, Burn.app offers two blanking methods: 'fast' and 'full'. 'Fast' simply erases the table of contents (TOC) from the CD-RW. This method is relatively fast and usually sufficient if you merely want to overwrite the CD-RW with new data. This method however does not erase the data from the disc. If you want to do this, you must select the blanking mathod 'full'. Note, that a 'full' blank will take significantly longer. Hence, this method is recommended only if you must make sure that all data is wiped out.
Selecting 'Tools'->'Blank CD-RW' will pop up the following panel where you can choose the blanking method:

Execute the fast blanking method.

Execute the full blanking method.

A status bar gives information about the progress.

Blanking will start immediately using the tools selected in the 'Burn Tools' panel.