Je vous ai informé au sujet de ceci in French means "I have informed you about this" in English.
"quoi à leur sujet" is "what about them" in French.
sujet »anglais
"Read all about it" can be translated to French as "Lisez tout à ce sujet" or "Tout savoir à son sujet".
sujet
Sujet.
Au sujet de and de for concerning, autourfor around, dans tous les sens for moving all around, and environ for approximately are literal French equivalents of the English word "about." The respective pronunciations will be "o syoo-zhey duh," "duh," o-toor," "daw too ley saw," and "aw-vee-ro" in French.
un sujet (masc.)
"Quel est ton sujet préféré?"
'quel est mon sujet?'
le pire sujet.
Ma matière préférée and mon sujet préféré are French equivalents of the incomplete English phrase "my favorite subject." Context makes clear whether academic (case 1) or theme (example 2) suits. The respective pronunciations will be "ma ma-tyer prey-fey-rey" and "mo syoo-zhey prey-fey-fey" in French.
If you mean people, there is no such thing. France being a democracy people are citizens, only people with royalty are subjects (English, Belgian ....)