Exactly...just means that the info you provide on that website should be safe.Wrong.
Try typing https://www.nike.com and see what happens.
If the "https" is green, that means the site passes basic security. If the "https://sitename" is highlighted in green, it means the site has passed major security tests. Keep in mind this may be applicable to the entire site but some people only install this on their e-commerce page(s).
And also keep in mind this is all in layman's terms...