Camera is Latin meaning “dark chamber”. When you open up the camera in the light, all the dark leaks out. Is the film spoiled? Most likely the pictures you took are ruined. There is a slight chance the first one or two you took will yield a partial image. This is dependent on how bright the ambient light and the length of time the back remained open. What could save the first few frames is the opaque coating on the back. This coat is called “anti-halation”, protects the film from exposure coming from behind. A halation can result if a bright object images and the light penetrates the film. This stray light can re-enter the film after reflecting off metal inside the camera. This film layer might provide you some protection.

Now a word to the wise: Unless the shots are significant, use this film as a sacrificial roll and practice, using it to help you learn how to load, advance frames, and rewind.