Farstrider camp is an outpost in Ashenvale. Night elf Rangers created this outpost from several large trees that were hollowed out and attached by suspension bridges. The night elves maintain regular trade with their people in Nighthaven.
It may or may not exist at the time of World of Warcraft, probably having been destroyed by the Warsong clan which was cutting the trees down in that area. Either that or it doesn't appear due to world scale issues. Maybe Night Elven Farstriders are Silverwing Sentinels and it means Farstrider camp is Silverwing Grove.