en_tn/2ki/07/05.md

at twilight

This refers to the early evening after the sun has set, but before it is dark.

the outermost part

"the edge"

the Aramean army hear a noise of chariots, and a noise of horses—the noise of another large army

The soldiers of the Aramean army heard noises that sounded like a large army approaching to battle them. This was not an actual army, but the Lord had made them hear these sounds.