The difference between "wie" "wen" and "wem" in german?

Answer 1

"Wie" means "how"
"Wen" means "who" in the accusative case.
"Wem" means "to whom" or "whom" (dative case)

For example:
Wie geht es Ihnen? (How are you?)
Sagen Sie mir, wen Sie meinen. (Tell me who you mean.)
Wem gehört das Buch? (Who does the book belong to?)

Answer 2

winnie2 is absolutely right so just a small addition:

"wie" can also mean "as" when comparing things - here an example or two
so groß wie - as big as
doppelt so viel wie - twice as much as

but
größer als - bigger than