Usage of ember generate command for addon

I have my Ember engine/addon which has package.json as below;

{
  "name": "my-addon-ui",
  "version": "1.0.0",
  "devDependencies": {
    "test-addon": "http://ift.tt/2tIjobI",
  }  
}

Also the package.json of the dependency test-addon looks like below;

{
  "name": "test-addon",
  "ember-addon": {
  },
  "keywords": [
    "ember-addon",
    "blueprint",
    "test-addon"
  ]
}

Now I see the following commands are used;

npm install
ember generate test-addon

While I understand what npm install does, I am confused about the usage of ember generate test-addon

What does it do exactly ? Does it map to the entries specified in keywords of "test-addon" ?

I am confused with the usage of ember generate without the type like

ember generate route OR
ember generate controller