If you are a specialist in cryptography, it is crucial to understand the difference between them. Otherwise, it is okay that you consider them as equal. A password is what you need to login into an account, a cipher is a series of code that keeps a piece of information from being seen by unauthorized individuals. A password is manually set by a user, while a cipher is generated by an algorithm, e.g. DES, IDEA, RSA, etc. In China, it is common that people confuse these two concepts. The correct Chinese translation of "password" is "口令", rather than “密码”, the latter is the correct Chinese translation of "cipher". Having little knowledge about cryptography, many Chinese people believe they enter "密码" when they login into their accounts, but in fact, it's "口令" or "password".

P.S. Traditionally--that is to say, a hundred years ago--a "cipher" meant a system that worked letter by letter. A "code" was a system that worked word by word. A "code book" was a volume like a dictionary, in which every word would be listed with its code. "London" might be given the code XQABJ, for example.

They are completely different. A "password" is a secret word or code or phrase that gives you access to something. Originally it was something a soldier needed to say so that a sentry or guard would let him in. "What's the password?" "Steelmill." "OK, you may pass." A computer password is something you type in. If the computer sees the correct password it allows you to use the computer. A "code" or a "cipher" is a method of secret communication. It is a method transforming a piece of text in such a way that it cannot be read, except by someone who knows the code or cipher. For example, a very rudimentary cipher is simply to spell each word backwards. Nac uoy rehpiced siht? Confusingly, the word "code" can mean both "a system for encoding," or "a single piece of coded material." For example, in the backwards cipher, "Nac" is the code for "can." So, sometimes a password is called "a code."