What is depicted on the Bayeux Tapestry?

According to legend, Pope Alexander II gave William the Conqueror a "guidon"

to take with him on his invasion of England in 1066 A.D. A guidon is a swallow shaped military banner, which flies on a single pole. In the famous Bayeux Tapestry a knight is pictured carrying this banner; historically he is identified as "E". Historians belief "E" was actually Eustace, count of Boulogne--an important ally of William.