The goal of mothur is to have a single resource to analyze molecular data that is used by microbial ecologists. Many of these tools are available elsewhere as individual programs and as scripts, which tend to be slow or as web utilities, which limit your ability to analyze your data. mothur offers the ability to go from raw sequences to the generation of visualization tools to describe α and β diversity.
If you publish research that uses Mothur you have to cite it as follows: Schloss, P.D., et al., Introducing mothur: Open-source, platform-independent, community-supported software for describing and comparing microbial communities. Appl Environ Microbiol, 2009. 75(23):7537-41