# Concept: Blocks

## What is a block?

_Blocks_ are individual pieces of your site's web page layout. They are placed
inside the regions (see [Concept: Regions in a Theme](/link/689)) of your theme, and can be created,
removed, and rearranged in the _Block layout_ (_admin/structure/block_)
administration page.  Examples of blocks include the _Who's online_ listing, the
main navigation menu, and the breadcrumb trail. The main page content is also a
block.

Some modules make new blocks available for placement on your site. For example,
when the core Search module is installed and configured, it provides a block
that contains a search form. You may also create and place your own custom
blocks.

Each block has its own configuration settings, which allow you to select
which pages of your site will display the block. It is even possible to place
multiple copies of a block, each with its own separate configuration and
visibility rules.
## Related topics

* [Concept: Regions in a Theme](/link/689)
* [Creating A Custom Block](/link/746)
* [Placing a Block in a Region](/link/747)