The impact of the development process on the developed software emphasizes the importance of software processes. Research works to control and improve software processes became thus essential. In this context, process patterns emerged as excellent artifacts, that perpetuate proved knowledge on software processes and enable its reuses in different situations. Although many researchers focus their interests on process patterns, this field remains insufficiently explored and much research is still needed. Thus, we give through this article a literature revue related to process patterns, and we compare important works in this field to highlight the progress and the difficulties yet to be addressed.