Archer and Marksman are level 2 creatures of Castle recruited from Archers' Towers.
"Archers and marksmen are lightly armored troops armed with crossbows for ranged combat and daggers for light hand-to-hand fighting. Marksmen can get off two shots in each ranged attack." RoE manual
Heroes with a specialty
Tactics and info
(This section contains a general opinion over the subject!)
They are critical in the early game, together with the Griffins, due to them being almost the only Castle ranged attackers, having good damage and also the marksmen's twice shot. However, with each ranged attack in a turn, the Marksmen will use up two shots, not one. Still, getting them damaged should be avoided, due to their hp and defense stats being equal and respectively lower than the level 1 Pikeman and Halberdier.
See also: