Who is Allah?
Allah is an Arabic word which means the Creator, the one who has created the heavens and the earth.  The word Allah is the most purest expression of the one who created the universe.  Allah cannot be made plural.   Allah is not a man, he has no gender, and he is not black or white.  Let us remember that Jesus Christ did not speak English. He did not use the word God when he called on his lord and Creator. In the English language when one refer to the Creator, the word God is used.  It is important to note that “Allah” is the same word that Arabic-speaking Christians and Jews use for God.  If you pick up an Arabic Bible, you will see the word “Allah” being used where “God” is used in English.  I find that a lot of non-Muslims get offended or think that Muslims worship something other than the Creator when Muslims use the word Allah.  If you ask the Christians who live in Egypt, Lebanon, and other parts of the world who's language is Arabic who created the heavens and the earth, they would say Allah. They are Christians and they use the word Allah because Arabic is their language.  There is a verse in the Holy Quran that Allah describe himself. When you read the verse, think about the one you worship and see if they fit this description.

Allah! There is no God but he-the living, The Self-subsisting, Eternal.
No slumber can seize Him nor sleep.  His are all things in the heavens and on earth.  Who is there that can intercede in His presence except as he permitted? He knoweth What (appeareth to his creatures as) Before or after or Behind them.  Nor shall they compass Aught of his knowledge except as He willeth.  His Throne doth extend over  the heavens and the earth, and He feeleth no fatigue in guarding and preserving them for He is the Most High, The Supreme (in glory).  Quran 2:255

This is the description of the one who the Muslims worship!