Final answer:
The phrase from the Star-Spangled Banner means that the light from the explosions made it clear that the American flag was still flying during the night, symbolizing the resilience and ongoing resistance of the defenders.
Step-by-step explanation:
The line "And the rockets' red glare, the bombs bursting in air, gave proof through the night that our flag was still there" from the Star-Spangled Banner can be put into more common English as follows: Because the explosions from the rockets and bombs illuminated the night sky, they revealed that the American flag was still flying despite the battle. This indicates that despite the ongoing bombardment, the defenders of the flag (and what it represents) had not been defeated.