There are many attributes as reflected by the Almighty God in the Quran where God refers to Himself sometimes with those attributes. These collectively have been called as Asma ul Husna أسماء الحسنى  or the Names of God. The scholars agree on 99 Names of Allah or the attributes that God has used in His book to describe Himself. "Allah" however is the ultimate name that God has used for Himself and rest all are His names that refer to His attributes.

While many scholars might disagree, from my personal knowledge i have found that the word Allah is not uniquely introduced in the Quran. The word Allah was used by Arabs (and also the Christians and Jews) of the arabian peninsula, to refer to what in english is termed as God, even much earlier than when Quran was revealed to the Prophet. It was used to point or reference to the one supreme ultimate being, the God of the gods of Kaba of the pre-islamic pagans. The pagans used to worship hundreds of Gods and Allah was their most powerful God of all of their idol gods. Islam explained the blasphemy and advised that Allah is the one and only, the unique, the Creator of all and everything, and explained His significance and place He deserves to be praised and worshiped alone without sharing. The most valid argument to support this statement is that the name of the father of Holy Prophet Muhammad (pbuh) was Abdullah (i.e. the servant/obedient/devotee of Allah). The word Allah is not a name in itself, but rather an attribute, a pointer meaning something like "The God" if you have to write it in the english language. Since there is no proper word in english to explain "banda"  or "abd" except for servant which is close but not proper meaning, there is no word in english to explain "God" in detail. Most english language origin was from christianity or atheists, the dominant groups of england, and both of which have very different understanding of the word God. Religion in english language comes from Roman latin origins, who had a totally different concept of God or infact gods. Understanding of arabic is required to understand the essence of the words Rabb, iLahi, Allah and Abd. However, it is also equally important to note that since the arrival of Quran and Islam as the complete religion, the word Allah is solely attribute to the one supreme being, and there is no one like Him.