Texts are conventionally divided into paragraphs. One way of marking paragraphs is to indent the first line like this.
Figure 1. Indenting
Another way is to leave a complete blank line between one paragraph and the next.
Figure 2. Blank lines
The white space created by the paragraph break has a considerable impact on the visual appearance of text. A page with paragraph breaks can be visually attractive while a page with no breaks can be quite intimidating. There are no hard and fast rules about the length of individual paragraphs because much can depend on medium, topic, audience and purpose; but in academic texts aim for an average of two to three paragraph breaks per page.
More important than visual appearance, however, is the effect paragraphing can have on content. Paragraphs give you the opportunity to organize the information you wish to give your readers into manageable, logical units so that they can see how you develop your argument as you move from one topic to another.
Exactly what constitutes a well-written paragraph is not easy to define. Nevertheless, some features are worth mentioning: point sentences, cohesion and coherence.