Lots of good stuff so far, but I feel like it's a bit focused on generating reports and analysis where Rmarkdown is really much more than just that.
Rmd files let you mix code (not just R, but other code engines as well) and markdown together to form publication ready documents.
In more layman terms, Rmarkdown can help you:
- write reports for work
- publish scientific journal articles
- write a book
- make a blog
- create documentation for your R package
- build an interactive dashboard
- document your analysis like a science lab notebook
- build a wiki
- create templates for homework assignments
- create templates for technical interviews
All of these options are possible just by adding a little bit of configuration options at the top of the Rmd file (such as title, author, theme, output file format, etc.), using markdown syntax to format your text (such as bold, italics, bullet points, etc.), and inserting "code chunks" to run arbitrary bits of code (such as make a plot using ggplot2 in R, run a SQL query against a remote database just by referring to the connection, perform some text manipulation in Python, etc.). The Rmd file is just a way to section off arbitrary bits of code from different other formats/languages, and the tool pandoc and R packages rmarkdown and knitr parse the Rmd file and build it into the document you want (defined in the config section at the top).
Hopefully you can see how useful Rmarkdown can be. If all you are doing is transforming bits of information and storing the results somewhere else, you might not need Rmarkdown. But if you have a story to tell with the results and want a flexible tool to help you tell that story in the way you see fit for the situation, Rmarkdown is going to be a great asset.