When we want to speak or write something in English, we always use the first word(s) to signal to the audience what the message is about. So in this case, first word(s) in speaking or writing is used to sign our sentence(s). In English, the first position in a clause contains textual meanings. Textual meaning is the meaning to organize our spoken / written text so that human make sense. Why do we have to analyze the text by using textual meaning? It is because when we use language we convey our meaning in spoken (phonology) or in written (graphology) so we have to analyze textual meaning to know what the kinds of text itself. To analyze textual meaning, we need a simple and distinct element of the textual meanings itself. The first element is theme and the rest of clause is rheme.

Theme is broadly speaking, what the clause is going to be about. And Rheme follows theme.
Theme represents ’this is what I am talking about’ and
Rheme represents ‘this is what I am saying about it’.

for further information, just call me.'_"