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.
English is the most commonly taught second language in the country and nearly everyone speaks at least a minimal amount of English if they are not completely fluent. Among the immigrant groups dozens of additional languages are spoken, including Persian, Hindi, and Urdu, but again many of these people speak either English or Arabic as a means to communicate across linguistic groups.
Religion
Nearly 80% of Qatar's citizens are Muslim, although less than half the population is citizens. Christians make up about 10% of the citizen population and the rest of the citizens adhere to numerous other faiths. Among the non-citizens, most are Muslim, Christian or Hindi.
Islam (the name of the religion, whose followers are called Muslims) is a monotheistic religion, whose holy book is called the Qur'an. The Qur'an is believed to be the word of God spoken through the prophet Muhammad from 609-632 CE (Common Era is preferred over AD (Anno Domini or "year of the Lord") since the Islamic world doesn't believe Jesus was the messiah). Islam believes Muhammad was the last prophet sent to earth by God, the last in a long line of prophets, which includes Moses, Abraham, and Jesus among others.