Achtung!
The accepted answer answered my question at the time, but is now outdated. Back then grunt-cli used grunt, but with another branch.
The not-accepted answers will tell you how it is today.
Question
What is the relations and differences between grunt-cli and grunt?
It seems to be the same thing, but different versions.
Grunt
https://npmjs.org/package/grunt
https://github.com/gruntjs/grunt
Grunt-cli
https://npmjs.org/package/grunt-cli
https://github.com/gruntjs/grunt/blob/devel/docs/getting_started.md
You’re correct, the two projects exist because of different versions of grunt.
grunt-cliis used for grunt version 0.4 (and has an explicit dependency on 0.4), which as of this writing is in alpha development. grunt-0.4 splits the command line interface (grunt-cli) from the API libraries.The “Getting Started” documentation you found is in the
develbranch of the grunt repository, which will be the 0.4 release.If you’re using grunt 0.3.x, then you don’t need to install
grunt-cli.