The Destination Panel is the lower part of the save window, and is used to select where and how the table or tables should be saved.
The Output Format selector is used to choose the format in which the table will be written from one of the supported output formats. The available selections are somewhat different depending on what it is you are saving; for instance some formats cannot accommodate multiple tables, so these formats are not offered for the Multiple Table save. If the "(auto)" option is used, an attempt is made to guess the format based on the filename given; for instance if you specify the name "out.fits" a FITS binary table will be written. Usually just using (auto) or selecting one of the listed options will be appropriate, but you can type into the selector a more specific value with configuration options, for instance votable(format=BINARY,votable=V12); see the output format descriptions in Section 4.1.2 for more details.
You can specify the location of the output table in these ways, which are described in the following sections: