easterly and eastern, what's the difference?

The easiest way to think about it is that 'eastern' usually means 'to or from the east' and is used to denote position relative to something else, whereas 'easterly' usually means 'with the character of or like "east" (the direction, rather than the place)' and is used for the direction that something is in. There are two main ways in which the word 'east' is used. One is the compass direction and the other is used to refer to the position of countries on the globe (relative to the meridian). It is usual to write the first with a small 'e' and the second with a capital 'E'. Here are some examples of usage: "The three Wise Men came to visit Jesus from the East. They were Eastern kings and they travelled in a westerly direction to reach Bethlehem. When they went home, they travelled in an easterly direction." "The ship travelled east, tacking against an easterly wind" [an 'easterly wind' is from the approximate direction of the east, not necessarily due east.] "There is more poverty in Eastern countries than in the West." "Ginger and cloves are Eastern spices. They come from countries in the East, such as India and the Malay Peninsula." "New York is an eastern city [on the east coast of America]. If you travel there from Los Angeles, you will go in an easterly direction."

Easterly is specifically directional, Eastern may refer to direction or, for example, to people or items from countries in the east or by extension to anything that is associated with such countries all the best urban