The foundation of Islamic teaching begins with God, whom Muslims call Allah. The name Allah comes from the Arabic language and means literally the one and only God. The Quran itself declares that Allah is the same God that spoke to the Jews and Christians. Therefore, when Muslims speak about God, they have in mind that it is the God of Abraham, Moses, Jesus and Muhammad (peace be upon them all). Even Arab Christians, who speak the Arabic language, say “Allah” when they talk about God or when they read their bible.
The Qur’an states:
“Tell [the Jews and Christians], ‘We believe in the revelation which has come down to us [the Qur’an] and in that which came down to you [the Torah and Gospel]; Our God and your God is one; and it’s to Him we surrender.’” (Qur'an29:46)
Allah is a unique term with no plural and no gender. It predates Muhammad and was also used in the form of El, Elah or Elohim by David, Moses, Jesus and other messengers of God, peace be upon them all.
He is God, the One that there is no deity but He; the Knower of the unseen and the apparent; He is the Source of All Mercy, the Merciful.
He is God, the Creator, the Maker, the Fashioner. To Him belong the most beautiful names. All that is in the heavens and the earth magnifies Him; He is the Mighty, the Wise." (Qur'an 59:22-24)