If you are an actual engineer you will have an engineering license that you took an engineering test to get.
Your licence will be governed by your states board of registration and under a separate branch with a board of registration that has engineers and surveyors on it ( usually about a two to one ratio favoring engineers ).
You will have special laws and administrative code that govern your actions and ethical behavior.
Absolutely NOT true...not all Engineers are Licensed...does not mean they are not an engineer. If you come out of college with an engineering degree and work for a company as an engineer...then you ARE an engineer.
There are even some engineers (not many)....mostly old timers...that do not even have degrees....but VERY far and few between.
A P.E. (Professional Engineer) is an engineer that has worked a minimum number of years under another P.E. (usually 4 years) and passed the National Board Exam.....most engineers do not need this to do their job....or to work as an engineer.
I work for a Consulting Engineering Firm and I am a Licensed P.E......and it is very valuable (to me and my employer) and practical to be licensed as a Consultant because it allows me to Stamp Drawings that Require a Professional Engineer to certify.