Jabberwocky

There are plenty of things that I don't understand.
Like how inverting and multiplying a fraction on a fraction makes much sense.
I don't understand why Lucy the dog always licks herself.
I don't understand the following poem stanza by Lewis Carroll:

'Twas brillig, and the slithy toves
Did gyre and gimble in the wabe;
All mimsy were the borogoves,
And the mome raths outgabe.

         (From "Jabberwocky")