A Song of degrees. In my distress I cried unto the LORD, and he heard me. In my distress - Through the causes afterwards mentioned.
I cried unto the Lord - Made strong supplication for help.
And he heard one - Answered my prayer by comforting my soul.
It appears to be a prayer of the captives in Babylon for complete liberty; or perhaps he recites the prayer the Israelites had made previously to their restoration.