What is Faith
Earlier I said Faith is unquestionable belief. True for any religion it is mandatory. If someone says that a religion is based on facts start questing them. Here is why?
First and foremost all religion talks about life after death. Either it is rebirth or raise to heaven or hell. Do anyone has solid proof for it or so called "Facts" the answer is a big NO. So fundamentally it is "Faith" like setting an alarm to wake the next day.
So let's ignore death and life after death for now and look into other beliefs.
1. Christianity "Virgin Mary" and "Resurrection of Jesus" both one has to have faith you can't dig into facts here.
2. Hindu's dwell in faith of God having extra heads, hands etc.
3. Jew's the great exodus splitting of red sea.
4. Jain and Buddhism are relatively free from miracles it's more of way to live.
5. As far as Islam is considered it is split across two lines one believes in miracles and the other believes in word of God.
Conclusion:
But All believe in one thing in common that is "A LIFE AFTER DEATH" without which no true religion can exist. So faith means to accept what cannot be proved as"Facts" or accept what one can not prove irrespective of his best efforts.