One could imagine that such a basic question does not warrant its own article. It just means 'to believe,' right?
No. No it does not.
When Christians say they are saved by faith in Christ it is not a mere acknowledgement that Christ is real and actually came to live, die and rise from the dead. Those are historically provable facts. It is also not the admission or realization that He is a great Savior. Both of these aspects are necessary to saving faith, but they are not sufficient.
Then what makes saving faith different?
Imagine, if you will, that a ship you were on has just sunk. You have no life jacket, and around you on all sides are bits and pieces of the ship, none of which are of sufficient size to save you. You see people likewise in the water and some of them are placing their faith on planks and random items that are adrift in the water. You witness their struggle and realize that what they are trusting on is not satisfactory.
Then you see in the distance one of the ship's lifeboats. You hear someone next to you call out, "We're saved!" You look over to him, bobbing in and out of the water, and remind him that he is still not in the boat.
"But I know that boat! It's strong and true. It will never sink and those who are near it are safe."
You both begin swimming over to it, driven by the familiarity and promised safety. Arriving to it you place your hands on the side and begin pulling yourself in.
"What are you doing that for?" He asks, "You already know this is the lifeboat, right? What need have you to climb in? If there arises trouble, we are right here with the lifeboat."
"But, are we not in trouble already?" You ask.
He replies, "Well, yes, but that is why we are here at the lifeboat." He knocked on the side of the boat, "Look how solid the craftsmanship is! This really is an amazingly sturdy lifeboat that could hold up to the greatest of storms; there really is no need to look for another lifeboat, this is the only one for me!"
Climbing in, I looked back to him and asked, "Don't you want to get in?"
"No," he said, "I am happy just knowing that I found this lifeboat."
The differences between people's definitions of faith can lead to some of the most destructive heresies in the church. When it comes to definitions, few could ever tell you properly what faith itself is, nor how efficacious faith is contrasted with dead faith.
The illustration above is one that focuses on the two misconceptions of saving faith, and the one example of saving faith.
First, we have the easily dispelled notion of "believe on whatever you want, just be sincere about it" crowd. These are those who, in that shipwreck, placed all their hope and trust (faith) on random pieces of wood that were insufficient to save them. This would be an apt description for anything but Christ.
Second, and much more common among the assembly of saints, are those unsaved who think themselves saved because they admit Christ is the Savior. Good for them, even the demons believe such. This is the man who swims with all his might to the lifeboat, throwing off all other hopes, but instead of getting into it he merely studies it. Appreciates it. Talks about it.
Third, and the rarest of all, is the only saving faith. They will not trust in other things, they learn and admit that Christ is the Savior; and then they trust Him to save them by being "in Christ." In the metaphor of the lifeboat, it is the one who climbed in that actually experienced salvation, not the one who simply admitted the reality of the lifeboat's existence and power.
How quickly are some evangelists satisfied with a mere admission of Christ's ability and power to save!
For salvation, one must place their trust, their hope, their all in Christ.
Recognizing a lifeboat's ability to save while remaining in the water will not save you in the least.
Get in the boat.