What is the difference between below two pieces of code?  

Code 1

```
$block = $this->getLayout()->createBlock('CLASS_GROUP_NAME/PATH_TO_BLOCK_FILE')->toHtml();
$this->getResponse()->setBody($block);

```

Code 2

```
$block = $this->getLayout()->createBlock('core/template')->setTemplate('PATH/RELATIVE/TO/TEMPLATE/*.phtml')->toHtml();
$this->getResponse()->setBody($block);

```