HTTPS is the method of communicating securing on web pages. When you look at the address and you are going to communicate secure information or things like your social security number, bank account numbers, etc. you want to make sure the address in the address bar starts with https instead of http. HTTPS is also used for things like taking tests online.
HTTP is hypertext transfer protocol and is the rules most web pages use when they are transmitted across the Internet. The information can be easily read in transmission by anyone wiretapping.
HTTPS is secure hypertext transmission protocol. The word secure comes first but the s comes at the end of the acronym. When the https protocol is used the information is encrypted (put in a format it cannot be easily read) when it is sent across the media. Using https makes your transaction secure and you don’t have to worry about the information being stolen and misused.
HTTPS makes your transaction basically secure. It is not absolutely secure, but makes it very hard for anyone to determine what the data contains.
Make sure when you are doing web transactions that the address bar has an address that starts with https. Most browsers will show a lock by the address if it using https to tell you that your transaction is locked or secure.