There are several different types of journal manuscripts, including Rapid Communications, Original Research, Review Articles, and Case Studies.

Original Research:

This is the most common type of journal manuscript. It may be called an Original Article,Research Article, or just Article, depending on the journal. The Original Research format is suitable for many different fields and different types of studies. It includes full Introduction, Methods, Results, and Discussion sections.

Rapid Communications:

These papers communicate findings that editors believe will be interesting to many researchers, and that will likely stimulate further research in the field. Rapid Communicationsare usually published soon after submission to the journal, so this format is useful for scientists with results that are time sensitive (for example, those in highly competitive or quickly-changing disciplines). This format often has strict length limits, so some experimentaldetails may not be published until the authors write a full Original Research manuscript.
Many journals also refer to this type of manuscript as a Letter.