Blocks are the boxes of content (such as "User Login" or "Who's online") that can be displayed in regions (such as footer or sidebar) on your page.
Blocks are made available to your site most commonly by enabling modules. Once created, a Block can be modified to adjust its appearance, shape, size and position - or which Website pages it appears on.
There are some cases where you want to render block within content of page or part of node body. Here is sample code to render the blocks programmatically in Drupal 7.