The chances are that this is the first time you’ve seen the OTP acronym. OTP is one of possible replacements of static passwords. Instead of remembering your password, you need to have a device that will compute a new OTP code each time you want to log on to a server. You will also need a different OTP “generator” for each server or web service that uses OTP and you will most likely still have to enter your password (or a shorter PIN) as well.
One time passwords are short numeric strings of a fixed length. Each time you want to log on somewhere with OTP, the string you enter will be different. The OTP string would change with the time or after each time you use one OTP value.