I've heard a lot of different teachings about faith , but this is how I have eventually come to perceive it.
My views are certainly not the authority, but I'll share it with you.
Faith is a commitment to your belief.
The less evidence there is to support your belief, the greater the faith required to commit.
When you commit to a belief, you make choices. Your actions are affected.
Faith is the substance of things hoped for, the evidence of things unseen.
Lets say a guy asks for a loan at the bank. The person reviewing his application, interviews the guy and asks, "if I grant you this loan, will you pay it back?"
"Absolutely" the guy replies.
"How can I be sure, that you'll deliver?" the banker asks.
"My word is my bond" the borrower offers.
To the lender, that doesn't sound like much to go on, but he agrees to grant the loan anyway. He had faith in the guy.
The guy got the loan and was faithful in paying it back. Being faithful means you give a person a reason to fully put their faith in you.
When someone says, "God is faithful", they could be just feeding you a line that makes them sound spiritual, or they could actually be referring to a time, or a number of times, where by appearances, they were going to sink, but they trusted that they would be taken care of, and somehow, things fell into place at the 11th hour. Those kinds of experiences increases a person's faith the same way your faith would increase in a person who always kept his promises.
Now if the banker said," I believe that you can and will pay back this loan if I get it cleared for you, but I don't want to take chances."
That would be the opposite of faith. Not doubt. Not fear. Doubt can test beliefs and lead to fresh faith, fear can arise from negative belief.
Believing but not acting or committing is the opposite.