You say in this lesson that hashing passwords is a good way to protect from stealing of passwords stored online. But since you cannot reverse hashed passwords, what is the point on having stored online the hashed passwords that you may have forgotten as you are not able to unhash it back?
Correct you can not reverse them. But you can compare them. So if I want to know if your password is correct I hash the value you give me and see if it matches. If it matches I can authenticate you as you. Hashes help prevent people knowing your real password. It doesn’t stop them stealing the hash. There is a whole section on this in volume II. Check that out.