Islam was the religion given to Adam The first Man on Earth who was created by God, not as fallen being. All The Prophets & Messengers of God "Allah" to humankind on Earth were Muslims including Adam, Abraham, Moses, Aaron, Jacob, Jesus and Mohammad. They have the same basic Message to Mankind: "La Ilaha Illa Allah" which means no God worth of worshiping Except Allah and anything else is his servant and creation.
Although those prophets came with different books, practices and methods of worshiping, Prophet Mohammad (peace and blessings be upon him and all other prophets) was the last Messenger of Allah On earth Before the Day of Judgment.
The Basic Message of Islam is the absolute Unity of Allah 'God' and he is not independent on anything or anyone else or even alike, he is not three on one nor father and son, Muslims beliefs on Jesus as Allah's Prophet and Messenger and his servant just like all other prophets Including Mohammad and Moses.
Islam believes that God and his creations are completely different entities. Allah is not his creation nor he is a part of it. Islam believes that his essence and his great knowledge are everywhere on his creation.
Islam calls the human away from the worshiping of the creation of Allah and invites him to the worshiping of the creator -- Allah himself, because the greatest sin of humanity is the worshiping of the creation.
Among the basics of Islamic Religion, the most important part is the belief in one God 'Allah' and He is the only Creator, Ruler, Lord, Administrator and Master of all that exists, And this Universe exists and functions because the will of Allah alone.
Allah responds to man's prayer and He is the only one who has the power to accept or reject it. He is the Master of man's destiny, no one ever else can interfere with the fate of others or even with his own fate!
All the humans hopes and fears should be only directed to Allah. He is the object of fear & source of favor.
That's the bedrock and most fundamental aspect of Islam religion, May Allah guide all of us to the truth and thank you for your time.