closed bolt = when the bolt inside a gun when at rest and ready to fire is past the breach opening (feed neck) and when the gun is fired the bolt moves back so a ball can drop in and then be fired.
so firing cycle = bolt forward .... trigger pull bolt back .. after fired it stays forward
open bolt= when teh bolt in a gun is at rest ready to fire at the back of the breach and allows the feed neck hole is clear do the ball drops in and when the bolt fires it fires the ball and returns back to its postion ..
so firing cycle= bolt back... trigger pull bolt forward after fired goes back
hope this helped