:salamext:
Fitnah is like a trial or tribulation, what's going on in the muslim world today is a big fitnah aswell.
The word Fitnah comes from the root word: Fitaan, and that's the job of the blacksmiths [the ones who heat metal.] What the blacksmiths do is that they get metals, and they burn them at a really high temperature, and then they separate between the good part of the metal (like gold for example) and the bad (like the waste metal.)
The same way Allaah tests us through trials, and then this test distinguishes between the true believers who have strong faith in Allaah [and their like the gold metal - precious] - whereas the waste metal is like the people who pretended to be believers, and never really placed their trust in Allaah, so they failed the test/trial/fitnah they went through.
Allaah says in the Qur'an:
Alif. Lam. Mim.
Do men think that they will be left alone on saying, "We believe", and that they will not be tested?
We did test those before them, and Allah will certainly know those who are true from those who are false.
[Qur'an Surah Ankaboot (The Spider) 29: 1-3]
Do you understand? And Allaah knows best.