Can someone tell me what this means?

Its a certain range level that you are able to read on. Examples: 10th grade reading level5th grade reading leave etc..

Explanation:

Beowulf and Grendel are antipodes - completely opposite characters. Neither of them is immortal, so they can fight each other. While Beowulf is a fearless warrior who came to save King Hrothgar's realm from menace, Grendel is a monstrous, bloodthirsty villain who enjoys killing and eating people. Grendel comes, "bearing God's wrath" because he is a descendant of Biblical Cain, who killed his brother. Even though he has a human shape, he is irrational like a monster:

"The monster had no thoughts of delay,
But swiftly seized the chance given,
Grabbed a sleeper, and tore him apart,
Bit to the bone, drank the heart’s blood,
Swallowing swathes; soon he’d eaten
That dead man, consumed him utterly,
Head to foot."

But Beowulf has another defining quality of a hero - enormous physical strength, so he rips Grendel's arm off, which will cause the latter's death.