Ghostscript is a package of software
that provides:

An interpreter for the PostScript language,
with the ability to convert PostScript
language files to many raster formats,
view them on displays, and print them on
printers that don't have PostScript
language capability built in.

An interpreter for Portable Document
Format (PDF) files, with the same abilities.

The ability to convert PostScript language
files to PDF (with some limitations) and
vice versa.

A set of C procedures (the Ghostscript library)
that implement the graphics and filtering
(data compression / decompression / conversion)
capabilities that appear as primitive operations
in the PostScript language and in PDF.

For information how to use Ghostscript see
/usr/share/doc/packages/ghostscript/Use.htm