npm init creates package.json npm install grunt --save-dev -> is added dependencies to package.json file. { "name" : "sample-test" , "version" : "1.0.0" , "description" : "generated for grunt json" , "main" : "Gruntfile.js" , "dependencies" : {}, "scripts" : { "test" : "echo \" Error: no test specified \" && exit 1" }, "author" : "" , "license" : "ISC" , "devDependencies" : { "grunt" : "^1.0.4" } } npm install grunt-autoprefixer --save-dev { "name" : "sample-test" , "version" : "1.0.0" , "description" : "generated for grunt json" , "main" : "Gruntfile.js" , "dependencies" : {}, "scripts" : { "test" : "ech