What is tribulation?

Affliction ( al-ibtila') is a trial and a test, encompassing both good and evil, as stated in the Almighty's words: "And We test you with evil and with good as a trial; and to Us you will be returned." This world is a realm of trials, and these trials have purposes, among which are: expiation for sins, elevation of ranks, purification of believers, or they may be a punishment for sins.