In the general sense faith is equivalent to confidence and trust. In a religious sense it means believing in the unknowable or the ineffable. But to a Sufi it has a most practical application of all, for the Sufi says, "Trust in Allah but tether your camel."
Something you truly believe in. No matter what doubters can say, you always believe in it. Like God. Some say he's real, other said he's not and that the world won't end, which it didn't so they were right on something. But I believe that God is real, and Mayans are stupid when is come to world tragedies.
Used in a religious perspective, faith is complete nonsense and leads people to be illogical and in denial. It is equivalent to trying to fight in the roman colosseum with no arms and thinking you're going to win.
Religious faith is believing with absolute certainty that something is true or real, like God, or angels or an answered prayer or heaven, even though there is no evidence for its existence, just like the unfortunate delusional folks who are certain of their delusional reality. The difference is that if of large percentage of the population believe the same delusion it's called, "faith". - I recommend that you watch a YouTube video called "Are Christians Delusional?", by Richard Carrier. - Of coarse the logic can be applied to any other faith based religion as well since that is what the question is about.
Faith to me, means I have a certain strength, an indescribable desire, a trillion moments all connected to one life cycle that allow me to be alive in the presence of a higher being. Faith to me is living in that presence.