lp [-dprinter] filename...
lp sends a file to the printer spooling area, where it will be processed and printed.
The printer referred to by the lp command may contain filters. A filter is a program that formats data according to the contents of the file. For example, most PostScript printers, such as the Sun LaserWriter and the Apple LaserWriter, have a PostScript filter, which means that any file sent to the printer will be transformed into PostScript format (this is because the printer ONLY understands PostScript, a page formatting language). If a true PostScript file is to be sent to the printer, a flag would be used to bypass that specific filter.
The environment variable LPDEST could contain the name of the default printer. Any available printer is also accessible with the -dprinter flag.