If you’re an R user looking for more information on writing R for production use cases, this site isn’t really about that, so check the resources for writing production R page instead.
Understanding R and it’s ecosystem
The best place to start your journey towards understanding the world of R is the Field Guide to the R Ecosystem. It’s a concise, non-technical introduction to the language and supporting software. The guide presumes no previous knowledge of R or any other programming language and is aimed primarily at managers and IT professionals approaching the language for the first time.