"Twas brillig, and the slithy toves
Did gyre and gimble in the wabe."
In this passage, the speaker sets the scene of the poem, describing the surroundings. He points out nonsense creatures called "slithy toves." Although this is nonsense, the word "slithy" sounds like the word "slimy," which gives us an idea of what these creatures might be like. Similarly, "wabe" might suggest "waves" or "water". As such, although we don't understand the language here, we have some understanding of its meaning from the sounds.
“Beware the Jabberwock, my son!
The jaws that bite, the claws that catch!
Beware the Jubjub bird, and shun
The frumious Bandersnatch!”
Here, the protagonist of the poem is warned by his father to beware the Jabberwocky, who is described as a dangerous creature with vicious claws and teeth. He is also told to beware the "Jubjub bird" and the "Bandersnatch." Although the first stanza seems positive, we are immediately made aware of a sense of danger with the word "beware."
"One, two! One, two! And through and through
The vorpal blade went snicker-snack!
He left it dead, and with its head
He went galumphing back."
In this stanza, the protagonist kills the Jabberwocky and returns home with its head. The action of the fight is emphasized by the use of exclamation marks: "One, two! One, two!." The protagonist takes back the Jabberwocky's head to show his father, which is a symbol of his victory.