Language
Arabic is the only official language in Oman. The written form of the language is called Modern Standard Arabic (written in the Arabic script), which gives the language consistency across countries from a written perspective. The spoken dialects of Arabic are so drastic from location to location that Arabic speakers in Oman may not even understand Arabic speakers from a country further away, like Morocco. Obviously the dialect of Arabic in Oman is most closely related to the dialects spoken in nearby countries like Yemen and the United Arab Emirates.
Arabic is a Semitic language; other closely related Semitic languages include Amharic (Ethiopia) and Hebrew. More distantly related are languages like Berber (North Africa) as well as historic languages including Phoenician and ancient Egyptian.
There are a number of ethnic minorities that speak less common languages, including Baluchi, Urdu, and others. For most of these people, Arabic is also learned and is the most common language of communication between groups. English is the most commonly taught second language in the country and many young people speak at least a minimal amount of English if they are not completely fluent.
Religion
Ibadi (or Ibadhi) Muslim is the official religion of Oman and nearly three quarters of the population follow this religion. The rest of the population is also primarily Muslim, consisting of Sunni and Shia Muslims, but also smaller numbers of other religions, including Hindi.