Some people mistakenly think that Allah is the "god of the Muslims," and a few even like to claim that Allah is an Arabian moon god, but the word Allah is simply the Arabic word for God. Every language has a word for God, and Arabic is no exception. If you have any doubt, you can check an Arabic translation of the Bible, you will find that it uses the word Allah. In fact, since Arabic is a Semitic language like Hebrew, the language of the Torah, and Aramaic, the language spoken by Jesus (pbuh), you'll find that the words for God in those languages, El in Hebrew and Alaha in Aramaic, are very similar to the word Allah. This just goes to show that Allah is the same One God, the Creator of the Universe, loved and worshiped by all of God's prophets.
"He is Allah , the Creator, the Inventor, the Fashioner; to Him belong the best names." -Qur'an 59:24