What is Islam?
Islam is submission to the will of Almighty Allah through the principles of monotheism, obedience, compliance, and acceptance of His laws.
The Messengers were sent with a unified message: to worship Allah alone without associating any partners with Him.
Islam is the religion of all Prophets; each conveyed the same message with distinct laws. Presently, Muslims are the sole adherents to the genuine religion revealed to all prophets. The current message of Islam is considered the truth, as the same Lord who sent Abraham, Moses, and Jesus is also the One Who sent Prophet Muhammad, the Seal of the Messengers. And the laws of Islam supersede and abrogate all preceding ones.
Contrary to Islam, contemporary religions are either human-made or divine religions corrupted by human influence. They have evolved into a blend of superstitious beliefs, inherited myths, and human interpretations. The Muslim Creed stands as the only uncorrupted belief system, and the Holy Qur'an has a single and unified version across all Muslim countries.
Allah Almighty says in His Holy Book,
قُلْ آمَنَّا بِاللَّهِ وَمَا أُنْزِلَ عَلَيْنَا وَمَا أُنْزِلَ عَلَى إِبْرَاهِيمَ وَإِسْمَاعِيلَ وَإِسْحَاقَ وَيَعْقُوبَ وَالْأَسْبَاطِ وَمَا أُوتِيَ مُوسَى وَعِيسَى وَالنَّبِيُّونَ مِنْ رَبِّهِمْ لَا نُفَرِّقُ بَيْنَ أَحَدٍ مِنْهُمْ وَنَحْنُ لَهُ مُسْلِمُونَ (84)وَمَنْ يَبْتَغِ غَيْرَ الْإِسْلَامِ دِينًا فَلَنْ يُقْبَلَ مِنْهُ وَهُوَ فِي الْآخِرَةِ مِنَ الْخَاسِرِينَ 85)."Say, "We believe in Allah and what has been sent down to us and what was sent down to Abraham, Ishmael, Isaac, Jacob, and his descendants, and what was given to Moses, Jesus, and other prophets from their Lord; we make no distinction between any of them, and to Him we submit.*Anyone who seeks a religion other than Islam, never will it be accepted from him; and in the Hereafter he will be among the losers."
[3: 84, 85].