“The raiding parties came out of the camp of the Philistines in three companies.” The Philistines were overconfident and arrogant. They had a large enough army to attack Saul’s camp, and if they killed him and much of his army the rest of Israel might have fallen to them. Instead, confident of their future victory, they decided to harras Israel and demoralize them with raiding parties.
“one company turned to the way that leads to Ophrah.” This raiding party headed north.
“land of Shual.” Literally, the land of the Jackal.