sola fide means "faith only". most protestants believe that people must trust jesus. they have to trust that jesus brings people back into relationship with god. christians believe that sin creates a gap between people and god, and jesus, who was perfect, died, taking the punishment for sin in place of people, bridging the gap. this is called salvation because jesus 'saves' people from a life and afterlife without god. the idea of "sola fide" means that trust in jesus is the only way to get salvation and finally get into heaven after death.