Can you be more specific as to what info you need Komn?
As for definitions Great circles are circles whose diameter and centre is that of the earth itslf. I.E. The equator and any line of longitude. If you cut the earth perfectly in half each circumference would be a great circle. Apart from the equator no line of latitude is a great circle.
Rhumb lines are straight lines which cross lines of lontitude at the same angle. Great circle lines cross each successive lines of long. at different angles and is the shortest distance between 2 points on earth
If you bang it into any search engine you'll get links to sites which explain it better than me.
Thats what I rememeber anyway. Shoot me down folks as my memory aint what it used to be
