What follows is strangely enough harder to find than it should be nowadays. Its a brief but holistic overview of what Muslims believe, and is essentially the framework by which Muslims view the universe and existence. Sure, Muslims believe in the Five Pillars, but knowing that alone doesn't really capture the essence of Islam. And so, here it is, a brief overview of Islamic theology:
Basically, 99% of Islam is the belief that there is One Supreme Being and Creator that is entirely other than the universe, and upon which the entirety of the universe is dependent. Man was given, and we accepted, the responsibility of intellect and the ability to acquire knowledge of all things. We have the ability to know our universe, as well as to come to know God. Before this life, every human was asked by Allah, our Creator, "Am I not your Lord?" to which we all testified "Certainly." The memory of this is not with us, but belief in Him is ingrained within our natural disposition.
In addition to this honorable blessing of knowledge, we were given free will, a hefty responsibility that was offered to much else of creation, but they refused to accept it. Now we are placed in this world with one sole purpose, which is to worship God. And the only two things man is responsible for is his free will, and sincerity. Everything is under Allah's control, but we are told to use this free will to do good works for His sake. And this entails believing in Him (along with His Angels, Books, and Prophets), as well as living life and regulating the Earth as He commanded.
As for who He is, we believe He is One and don't associate any partners with Him. He was the first and is Ever-Lasting, entirely Self-Sufficient, All-Knowing, the Most Merciful, the Loving, yet also the Just. Any good deed done for the sake of God is worship, whereas good works devoid of belief in Him will carry little weight on the Day of Judgment because we were not asked to just do good. We were asked to fight our lowly selves and desires to do good for His Sake, whereas if you do good without belief in Him then you already received what you were intending when you decided to do the good work. Then after we die, we will be resurrected, and on the Day of Judgment we will be called to account for all of our deeds.
Everything will be taken into consideration justly, so people that had less will be reckoned easier, whereas those who were blessed with more will be asked about how they used each blessing. Then if you believed and your good deeds outweigh your bad, you will enter paradise by Allah's Grace. But if you die disbelieving, then you will enter hell, abiding therein (either forever or for eons upon eons, a difference of opinions on this). Finally, if you believed but did more bad than good, then you will have to enter hell to be purified but will one day enter paradise, though after a very long time. But as you can see, belief in Allah and not associating any partners with Him is paramount.
Last point, Truth and Knowledge is sent to mankind via messengers and prophets. We believe that Christianity and Judaism were also Islam, i.e. the same religion all calling to submission to God, but we believe that they have been changed by man over time. We also believe in the same prophets, though we don't believe they were sinful as in Christianity, and also believe Jesus is a prophet and not the begotten son of God. In fact, we believe over 100,000 prophets have been sent to mankind all calling to the worship of the same One God (peace be upon them all). Finally, we believe that the Prophet Muhammad, peace be upon him, is the final messenger of God, and that the Qur'an is the final Word of God sent to mankind and that it will remain unchanged since it's revelation. If you're interested, here is a clip of what the Qur'an sounds like:
Whether you're curious about what Muslims believe or you're seeking more meaning in your own life, keep seeking knowledge and Truth with a critical and open mind. It can help you on your journey, wherever you want to go.