Why is the 'sign' of trademark "R"?

Question

Like for example:

A brand of cookies with an R after the logo or mark

Cookiebrand R

You know? those small R's with a little circle around them? Why is it an R

Answer 1

"Registered" trademark

Answer 2

Trademark is TM the R stands for registered and has to do with registering logos and such, but its different than an actual trademark (I do not know how its different though).

Answer 3

Symbols

The two symbols associated with U.S. trademarks ™ and ® represent the status of a mark and accordingly its level of protection. While ™ can be used with any common law usage of a mark, ® may only be used by the owner of a mark following registration with the U.S. Patent and Trademark Office (USPTO or PTO) and designates such. The proper manner to display either symbol is immediately following the mark in superscript style.

Answer 4

It stands for "Registered"

Answer 5

It means that's a registered trademark & you aren't allowed to copy or use it else you'll be sued.