https://youtu.be/uduSAFL-DmE?si=r_xfRrJkqEAE0fIv Death is the end of someone's life. People die because sin entered the world through Adam and eve's disobedience leading to physical death. People also die to get ready for the judgement day because death is inevitable. In our human nature people die because of old age, as people age, their cells and organs gets weaker and also weaken their immune system which can attract sickness easily. Affliction of disease like heart disease and stroke is also part of the reason why people die. Cancer is another major cause of death with various types affecting different parts of the body. We have other infectious disease example hiv/aid's and malaria which can also lead to death.
Accident can also take someone's life, also by falling, and also food poisoning.
Death is a process where the body system gradually shut down, and is also inevitable, all we have to do is live a life that please God because the best death is old age death and someone who also died in Christ.
For people who follows God, death is just a transition to be God.