Read this excerpt from A Black Hole Is NOT a Hole.

Just outside the event horizon of a black hole, light's energy keeps it zipping along, like that fish swimming along the outer edge of a whirlpool. Although the black hole's gravity changes the light's path, the light doesn't swerve into the black hole.

What does the description help readers understand?

-why fish swim along the edge of a whirlpool
-what happens outside an event horizon
-how energy changes a light's path
-where light energy comes from