Everything that has ever come to existence or will come to existence is created by Allah alone. Allah is the Supreme Lord of all that you see or not see that existed or now exist or will come to exist. He is the Lord of the universes. He is One, without any partners. There is nothing like unto Him. Nothing happens except what He wills. He does whatever He wills. He created the universes and all its inhabitants according to His will. He, likewise, created men in earth and ordered them to obey Him and His messengers. This obeying is realized by following a set of rules given by Him which is Islam.
Islam is the prescribed way of life set by Allah for the human beings in this universe. You may call it a religion but it is the way of life that one should follow from the day of the birth to the grave. It is the way of life that your lord, Allah, has sent down to you for you to follow so that you can be successful here in this life and most importantly hereafter in the eternity. Remember that Allah is not in need of you or your prayer, it is you who needs Allah's constant mercy as you live. Allah, being the most merciful, has sent down the prescribed path to success so that you may earn Allah's forgiveness.
In every ages and every nation as Allah wished Allah sent one or more of His prophets to lead them to His path. These prophets taught the same message 'there is no god only Allah' and they ordered them to worship Him and no one else. As such, starting with prophet Adam, may Allah give him peace, all the prophets Noah, Abraham, Moses, Jesus, may Allah give peace to all of them, preached and taught the same message. Muhammad, may Allah bless him and give him peace, is the last of all the prophets sent by Allah. His prophet hood brings the end of revelation and finalization of Allah message to mankind. Thus making islam as we know it, the finalized manifest religion for mankind
There is no salvation outside of islam. To enter islam, you have to believe in Allah according to Qur'aan and sunnah. Than you have to affirm your faith by testifying that, 'there is no god ONLY Allah and that Muhammad(sws) is his slave and apostle.' The faith also must include that you believe in Allah's angels, divine books (The Qur'aan and Original script of Torah, Psalm and Evangel and others), prophets (Adam, David, Noah, Abraham, Moses, Jesus and all others known or unknown, may Allah bless them all), the judgment day, the good and evil of the divine decree, and the life hereafter.
You accept Allah with all the beautiful names and the qualities that belongs to Allah.
You accept to obey the rules and regulations that has been sent down to mankind through the prophets.
By doing the above you accept Islam and become a Muslim. Wherever you may live whatever you may do whatever color your skin may be, rich or poor, king or slave laws of Islam applies to you without any bias, without any exception what so ever.
Why a muslim does what he does not: the objective
The objective of a human being is to uplift his position in the divine perspective by cleaning up ones heart from the dirtiness of this world so that Allah may grant him/her the knowledge and wisdom. In order to uplift ones state of being one needs to follow the prescribed manner set by Allah and taught by Allah's messenger(sws). Without practicing these one is destined to ruin.
This brings us to the point to learn about what to do and what not to do.
Broadly speaking actions of a human being can be divided into five groups: Obligatory, Recommended, Allowed, Offensive and Forbidden.
Some of the major obligatory acts are Five daily Prayers (Salat), Fasting in the month of Ramadan (Saum), Purifying Tax (Zakat) and Pilgrimage to Makka (Hajj) and learn islam. Forbidden acts includes to steal, rob, commit illegal(extra-marrital) sexual acts, drink alcoholic beverages, consume addictive to drugs, kill another muslim, eat pork.
It is an obligation for every muslim to acquire the knowledge of islam atleast to the extent so that one is able to perform ones own duty towards Allah and His creatures according to Allah's rules. These includes the knowledge of how to perform the prayers, fasting, to know which food is allowed and which is forbidden and others which affects ones daily life. In general, islamic knowledge can be classified in knowledge of Qur'aan and its exegesis, knowledge of hadiths and its methodology, knowledge of islamic faith and its methodology, knowledge of islamic jurisprudence and its methodology and knowledge of tasawuuf (purification of heart).
Rules regarding all the actions are derived from the Book of Allah (Qur'aan) and the Sunnah of the prophet, may Allah bless him and give him peace. Righteous islamic community based on Qur'aan and Sunnah are called Ahl al-Sunna wa l-Jamaa. Scholars of Ahl al-Sunna wa l-Jamaa have derived the laws for common muslim to follow along with the clearly defined laws from the Qur'aan and Sunnah.
As consequences, it is obligatory for every muslim to learn the rules of islamic way to best prepare himself/herself for the servitude of Allah.