DnDResources.comA Ranger serves a cause. He has an ideal that sustains him through the cold, bleak, hungry days alone on the border, watching over simple folk who likely do not appreciate or even know of his efforts.
The cause may be the defense of a realm, the protection of innocent creatures, of the unspoiled land, or of a specific tribe. This in no way implies a specific alignment. An Evil Ranger may watch the boundary's of Mordor out of devotion to the Dark Lord. An Orc Ranger may scout ahead of the raiding party, committed to reducing casualties among his brethren by eliminating Elven snipers.