Most UNIX computers have some kind of print spooling system. This system may follow the Berkeley way of doing things (and is typically called lpr) or the SVID way of doing things (and is typically called lp). Other options are out there.
In a typical UNIX installation, there are multiple computers accessible from many different computers on a LAN. The LAN may have many servers set up for handling print jobs across the suite of programs, but typically there is only a single server for any given printer. In the context of UNIX print services, a printer can be a line printer (where the name derives from), a dot matrix printer, a black and white laser printer, a colour laser printer, a plotter, a facsimile machine, .... The print servers are generally set up with ``magic'' filters these days, which know how to print all the kinds of files a user might be interested in: compressed files, LaTeXor TeXsource files, LaTeXor TeXDevice Independent Files (dvi), PostScript, nroff - troff - groff - ditroff files, graphics files, .... Typically these filters will be set up to transparently ignore files which they can't decipher. This reduces the number of times you get garbage output.