PCV - Positive Crank Case Ventilation
http://en.wikipedia.org/wiki/PCV_valve
As for breather pipes - that predated PCV, where the engine vented combustion blowby and other gases directly into the atmosphere. That hasn't been the case in several decades - replaced with the PCV valve for controlling emissions and extending the lifespan of the engine (assuming you stay on top of the maintenance).
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2002 Corolla S, 1.8L 1ZZ-FE VVT-i
2003 Matrix XRS, 1.8L 2ZZ-GE, VVTL-i (RIP)
2009 Matrix XRS, 2.4L 2AZ-FE VVT-i
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