1)
What does this Mizmor discuss?
1.
Rashi: It is about Yisrael, who are "l'Shoshonah Bein ha'Chochim" (Shir ha'Shirim 2:2). The thorns puncture them, and David prays for them.
2.
Radak, Malbim #2: It is about Galus. It speaks in the singular, for the Klal [of Yisrael]. Or, each one of the Bnei Galus prays and cries over his afflictions.
3.
Malbim #1: It is when Avshalom was chasing David.