There is very little known about the author of the poem Sir Gawain and the Green Knight. The dialect in the poem leads to an origin in provinical England. Based on the poet's other poems that were written, the poet was indeed both a sophicated and urban writer. Although it is impossible to date this poem, it was most like written during the time of Geoffrey Chaucer.
The poem combines two plots - the beheading contest, with an agreement in exchange of attacks, and the temptation, an attempted seduction by an attractive lady on the hero of the story. The poem combines comedy and satire, as well as a profound Christian view of character and its destiny.
A symbol which is very important in this poem is the pentangle. According to the poet, the pentangle is a symbol of truth - the first of the chivalric virtues also present in Chaucer's knight in The Canterbury Tales. It is truth that is put to the test in Gawain's search to find the Green Chapel where it is presumed he will die from a blow from the Green Knight. This, of course, does not happen. The only wound that Gawain receives is in his neck.
The poem is one of the latest and one of the best of the Middle English romance stories. It's greatness lies in the fact that it is a work of pure comic fiction, which is considered to be one of the biggest achievements of the Middle Ages.
Background Information from: Abrams, M. H. The Norton Anthology of English Literature. New York: W.W. Norton & Company, Inc., 1993.