Belief in Islam means
Belief in One God, Allah in Arabic.
Belief in all of God’s messengers. Belief in Prophet Muhammad (peace be on him) as His last messenger.
Belief in all the books sent down to His prophets. These books include Torah, Zabur, Injeel (Gospel) and Quran. The Holy Quran is the only divine book in extant today in the original revealed form.
Belief in the existence of angels.
Belief in the Day of Judgment, Life after Death, Heaven and Hell.
Belief in the Divine Decree or Predestination, its good and its bad.
It is a known fact that every language has one or more terms that are used in reference to God and sometimes to lesser deities. This is not the case with Allah. Allah is the personal name of the One true God. Nothing else can be called Allah. The term has no plural or gender. This shows its uniqueness when compared with the word god which can be made plural, gods, or feminine, goddess. It is interesting to notice that Allah is the personal name of God in Aramaic, the language of Jesus and a sister language of Arabic. The One true God is a reflection of the unique concept that Islam associates with God. To a Muslim, Allah is the Almighty, Creator and Sustainer of the universe, Who is similar to nothing and nothing is comparable to Him. The Prophet Muhammad was asked by his contemporaries about Allah; the answer came directly from God Himself in the form of a short chapter of the Quran, which is considered the essence of the unity or the motto of monotheism. This is chapter 112 which reads:
“In the name of God, the Merciful, the Compassionate. Say (O Muhammad) He is God the One God, the Everlasting Refuge, who has not begotten, nor has been begotten, and equal to Him is not anyone.”