This passage emphasizes that salvation is God's gift - a matter of grace. It would be impossible to overemphasize the fact that salvation is a gift from God - a matter of grace. The first is grace, the unmerited favor of God which provides salvation as a gift for all men. The second key word is faith, which is man's response to God's free gift. Now it becomes very important for us to understand what faith means.
Many people define faith as a mental acceptance of certain facts.
That is historical faith and we have historical faith about many things. We believe, for example, that certain cities exist and that certain people have lived though we have neither seen the cities nor known the people. That kind of faith, however, is not sufficient to save a man. Saving faith is something beyond the mental acceptance of the existence of God and of Christ. It is that, but it is more.