Justification by faith means being accepted by God based on faith in Jesus Christ rather than by any works or righteousness that we may have. It is through grace that we are justified, meaning that it is a gift from God that we receive by faith. This is in contrast to the idea that we can earn our salvation through good works or by following the law. In essence, it means that our faith in Jesus Christ is what saves us, and not our own actions or merits.