Nim offers a combination of three features: the efficiency of C, the expressiveness of Python and the flexibility of Lisp. There isn't a language out there that offers all of these in one package.
It's easy to get started with Nim because the advanced features such as generics and macros don't need to be used immediately. Once you learn the core concepts of the language it's easy to then learn a bit more about the more advanced features.
Nim can be used in practically every industry. Currently its been particularly well adopted for video game development, but it can be used as a replacement for C when writing software for microcontrollers or as a replacement for Python when writing web applications.