HTTP stands for Hyper Text Transfer Protocol. The main difference between http:// and https:// is the “s”, which stands for “secure.”
The address in the web browser most likely begins with the http://. This means that the web site is linking with the browser using regular “unsecured” language. It is possible for someone to “eavesdrop” or see information while on that web site; therefore, you should never ever enter your credit card number in an http:// website! However if the web address begins with https://, the computer is talking to the website in a secure code, and should be safe.