A+: Laser printers and their other components

 Printer Interfaces:
  Ethernet (max 330' of cable without an intermediate switch or bridge), USB (max 16' without a powered hub or special cable) and WiFi are the most common now, but others include parallel (old popular system, maximum of 50' using a very bulky cable), serial (very slow, also with a bulky cable), SCSI (rare), InfraRed ('IR'), Appletalk (no longer sold by Apple and slow), IEEE-1394 AKA Firewire (rare), and Bluetooth (33' max.).

Printer languages:
  If the computer has to send a dot-by-dot map ('bitmap') of each page to be printed, that's a lot of data to send down the wire. That's inescapable when printing pictures, but when you're sending a page of text   Therefore, printer control languages were created, so the data stream can be shrunk. The more powerful languages, such as Postscript, require more processing power in the printer control circuitry, shifting the printing burden from the computer and using a terse, elegant syntax, easily read. When laser printers were very expensive anyway, the extra cost of the Postscript language and its interpreter was an acceptable burden, but now that computers are wickedly fast and since people often buy on price, not elegance, the simpler, dumber printer is more popular, and PCL6 (developed by HP) now leads the pack as the predominant printer control language. GDI, another control language, is often the basis for even less expensive printers, with less text and more bitmaps sent from the computer to the printer. Since data transmission rates continue to rise with faster and faster networks and interfaces, the trade offs make sense.

Printer drivers:
  The manufacturer of the printer is responsible to create drivers, small programs, which allow other programs to create the datastream for the printer to use, and to communicate with the printer. Operating systems are shipped with drivers for popular printers, but as new features are added, the manufacturer must add to the drivers to enable the new features. 
  The feature set in the driver lets you determine the resolution, scaling, color vs B&W and other modes of printing as either the default or on a job-by-job basis.

  Paper quality is important to satisfactory printing. The composition (virgin paper vs. recycled content percentage plus rag content), weight and caliper (thickness) are all important to avoid jams.  The brightness determines how 'white' the paper appears. 

Other printing material:
  Make sure not to use any transparency or label stocks which were not specifically designed for your model of printer.