Drupal - Displaying Block in Template pages in Drupal

module_invoke()

Invoke a hook in a particular module.

Parameters

$module - The name of the module (without the .module extension).
$hook    - The name of the hook to invoke.
... Arguments to pass to the hook implementation.

Return value

The return value of the hook implementation.

For Drupal 7 :

$block = module_invoke('block', 'block_view', 16);

@arg 1 : module name
@arg 2 : hook name like block_view, block_info
@arg 3 : id or delta of the block e.g 16, map-block_1

for Drupal 6 :

$block = module_invoke('block', 'block', 'view', 6);

@arg 1 : module name
@arg 2 : hook name like block
@arg 3 : $op of hook_block e.g. info, view, configure
@arg 4 : id or delta of the block e.g 6, map-block_1