A: Solid line 50 meters from either try line.

B: Dashed lines 10 meters from half-line used to judge kickoffs

C: Solid lines 22 meters from either try line

D: Solid try or goal lines. The crossbars sit on this line.

E. Solid dead-ball lines, 10 to 22 meters behind try line

F: Dashed lines 5 meters parallel to the touch line for line-out zones

G: Dashed lines 15 meters parallel to the touch line for line-out zones

The orange player in the upper left wishes to join in the ruck but he is currently offside. In order to enter the ruck, he must circle behind the last man and bind in from the back side. 

On the other hand, the blue team is winning possession of the ball and wants to set up for an offensive phase of play. The blue player at lower left must set up for a pass behind the offside line; anyone ahead of the line cannot take a pass or influence the game unless he is onside.

Once again, the blue player in the lower left - let's say it's the fly half - must set up for a pass behind the Number 8 man.