A paragraph is a coherent text where the content is ‘about the same’. A section contains one main point (a key phrase) and the study, documentation, analysis or other that forms the basis for the key phrase; the coating (s) for the key phrase.
If the subject is held and something else unfolds, which is not a whole new angle or a whole new subject, then it is advantageous to make line breaks with indentation. A line break with an indent indicates that you are now moving on in the section, but you are not moving into something completely new. Remember the indentation in such a line break.
If, on the other hand, you change the subject or angle, then a new paragraph must be written, and because it is a new topic or a new angle, there must be a double line break, so that there is a line spacing between the two paragraphs. A new paragraph must start with a new paragraph leader and contain a new key phrase.
Paragraph are sentences that begin a paragraph and that just by being the initiators of a paragraph set the framework for what the paragraph is about. Thus, the paragraph leader is what should help create a red thread in your paragraph and is closely linked to the paragraph’s key phrase. It is by the introductory sentence that the framework of the section is set up.
Therefore, it has a vital importance for the reader to know what is going to happen and for the reader to follow what comes next. Some English teachers use the word ‘topic sentence’ about paragraph initiators.