Mature content in tag line... how does it get there?

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I must admit that I am confused about something... That "mature content" in tag lines. How does it wind up as a tag on posts? Do people choose to put it there or is it just that some words like "breast cancer" in other peoples post wind up causing it to arrive there. I am uncertain. I posted something about ways that we get or stay healthy and honestly was not putting any mature content in my post and yet it appeared in the tag line later. Is it something that myLot does when it sees certain words in a post or do those posting add it as a tag line themselves?