The short answer is that Muslims believe in an after life where we experience a different reality from this life. The Qur’an and Hadith, which are the sayings of the Prophet Muhammad, allude to the afterlife with metaphor that include imagery relating to reward and punishment. Understanding the complexity of our current life or reality is an important aspect when questioning the reality of the after life. It is not a simple issue or concept. Studying the Quran and the verses relating to the after life will help you to understand what Muslims believe.
Similar to other faiths, there is the aspect of judgement, reward, and punishment. Islam teaches varying degrees of each. Uniquely, Islam does not teach of indefinite punishment. There will be a time when no one will be left in hell. The concept of heaven and hell alludes to states of mind that are related to nearness or communion with God. Certainly, the Quran relates fire and burning, but it must be understood that the reality of the afterlife is not what we experience here. Our senses will be different, our bodies will be different. The concept of punishment and reward is something we experience in this life and perhaps suggests how it will be experienced in the afterlife.
The concept of peace and suffering are important in Islam. How one experiences paradise in this reality helps one to understand it in the afterlife. By following the teachings of Islam and worshiping God appropriately, an individual gets a sense of the benefits of aligning with God’s desires for us. When we stray from these teachings, we experience the consequences of our actions which lead us away from peace and tranquility.
Muslims do not believe that only they can attain God’s pleasure or paradise. There is no monopoly on God’s grace or mercy that is reserved for Muslims alone. God’s grace and mercy extend to all people. It is God alone who determines who gains or losses in the afterlife. God alone has the knowledge of our potential and what is required for us to establish a relationship with him. The punishment of disbelievers described in the Quran is of those who consciously and purposefully go against God’s teaching and warnings. A person ignorant of these matters would certainly be treated differently by the All Merciful. Nor is paradise guaranteed to anyone. Again, it is God who knows us and what we need in order to gain nearness to him and to fulfill our reason for creation.
Muslims do not believe our existence ends with our physical death. There is belief in the soul, and in experience a reality after this one. This after life is experienced according to our actions before death. One who is unaware of their responsibilities toward God would be considered lost and confused which be a type of hell in and of itself. There is also a reformation that may be required in order to begin recognize God. Muslims do not believe in reincarnation where one would return to this reality in a different form. Our souls do not return to other bodies in this reality.