v1: The scene returns to the battle between the Philistines and Saul's army. Israel retreated before the determined Philistine army (compare 4.9-10).
v2-3: Saul's sons were killed, as the Philistines attacked Saul himself. Jonathan died with Saul, remaining faithful to his father, in spite of Saul's rebellion against God.
v4-6: David had previously been Saul's armour-bearer. Had he been in the battle he may well have been killed. Again, God preserved His chosen King.
One can understand the choice of suicide, given the inevitability of defeat. Yet suicide is not the action of a godly man.
v7: The Philistines took a huge swathe of Israel, as the Israelite people fled from the nearby cities.
v8-10: The Philistines rejoiced, for they had suffered defeat for several years, particularly when David led Saul's army. See 2 Sam 1.20.
v11-13: The kindness of the men of Jabesh Gilead, see ch 11; Judg 21.8-12.