What are PCB Plug-ins ?

PCB Plug-ins are shared libraries for PCB.

What is PCB ?

PCB is an interactive Printed Circuit Board editor for the X11 window system.
PCB includes a rats nest feature, design rule checking, and can provide industry standard RS-274-X (Gerber), NC drill, and centroid data (X-Y data) output for use in the board fabrication and assembly process.
PCB offers high end features such as an autorouter and trace optimizer which can tremendously reduce layout time.