Question

Whats the different of Arabic and Urdu?

Answer 1

They do not belong to the same family at all. Urdu (similar to Hindi) is Indo-european, whereas Arabic is semitic.

Your question is like : "What's the difference between French and Vietnamese?"
'Better' question would be: "What do they have in common?".
Well, they share a common Arabic script, though Urdu borrows more from the Persian version.
Due to population contact and cultural exchanges, Urdu has incorporated some Arabic words and Arabic has some Persian words too, but probably in much fewer numbers.

Hope this helps.