Over the course of the three nights Gawain was there, the host was going to reward Gaiwan, if he rewarded him back, to test his loyalty. He hunted deer, boars and fox to give to Gawain. In return whatever Gawain got, he had to give to the king.
I will reward Gawain these animals.
Also over the three nights that Gawain was there, the host set up tests with his wife to see if Gawain would engage with her. The first two nights he was honest, but the third night he took the green girdle and didn't give it to the king.
What are you doing?
Gaiwan sets off to find the green chapel and comes across a really shrubby place. He realizes that this is the green chapel.
Is this really the green chapel?
He meets the green knight and he raises his ax and misses him. Gawain flinched which made knight question his authority. Then he misses gains and the third time he hits him but it just leaves a little scratch.
You are a coward.
Gawain then makes his way back home and his wound heals on the way. He then tells the court that he has to wear the green girdle over his shoulder forever as a sign of failure and sin. They decide that they will wear green belts of silk to show respect for his bravery.