There are at least seven types of paragraphs. Knowledge of the differences between them can facilitate composing well-structured essays. In order to write coherent essays, students need to learn about the basic functions of various paragraphs in college writing. Most paragraphs will have several functions to fulfill at a time and it is important to know under what circumstances their functions can be conjoined, if at all. Here is a site that can show us the differences among the seven types of paragraphs.
http://groups.apu.edu/practicaltheo/LECTURE%20NOTES/Shrier/8%20paragraph%20types.pdf