There are a lot of thees in the Charlotte's Web. Probably the biggest one is friendship. Friendship is big between a lot of the main characters (i.e. Wilbur, Charlotte, Fern, etc.).
One way friendship is visible in the book is just looking at Wilbur and Charlotte. It's pretty clear that Wilbur & Charlotte will be great friends. Their relationship just gets stronger throughout the book, to the point where Wilbur befriends the 3 children of Charlotte that stayed at the barn.
Fern & Wilbur also have a great friendship. From the beginning of the book, Fern & Wilbur are inseparable. They do everything togetyher. And even though they don't see each other as much towards the end of the book, they are still amazing friends to the end.
