Arabic is the language of Arabs. Persian is a language of Iranians. Urdu is a language of Indians. Urdu is similar to hindi. It is a variant of an Indo-Aryan language, Hindustani. These languages are different in their dialects, the meaning of their words and in the way they pronounce their words. There are also difference in using propositions.
All the 3 languages are writing in Arabic, this is likely the only similarity they share.
The biggest difference between the Arabic, Persian, and Urdu languages is that they all come from different areas. Arabic got its start in the Middle East and to this very day is the majority language that is spoken in the region. Where Arabic was a language that was spread and spoken all tthroughout the Middle East, Persian was a language that only was spoken in the area of Iran. Urdu is most closely related to India but also has its founding near what was the location of the Persian Empire.
While these languages could be said to be located in somewhat close and near regions, the completixty of the different languages allowed for so many different languages to be able to survive during the time period. There are also the differences in dialects, pronunciations, and the meanings of words amongst the three languages. All three languages are noted as being three of the oldest and cultural rich languages in the world today. All three are also widely spoken all throughout the Middle East and Arab regions.