Blocks are boxes of content that can be placed in certain regions on your page. You can manage blocks from under the site building area of the administration section. On this page, you can list the existing blocks or add a new block. Many modules also create blocks for you and they will also be listed on this page.
At the top of the list page is a list of all the different themes available to your site. You can changed the block settings for each of themes. Most likely, you will want to just change the block settings for your default theme.
Below the list of themes, and some explanatory text, is the list of blocks on your site. The list is sorted by the region that the block belongs to. You can specify the region the block belongs to with the first drop-down box after the block name. The most common regions you'll use are the left and right sidebars, but you can also put blocks in the header, footer and main content area. If you'd like to save your block, but not have it be in any region at the moment, then you can select <none>.
Following the region drop-down is another drop-down, this time for the weight. After the weight is a link to configure the block. If the block is one that you creates, instead of one created by another module, then there will also be a delete link here.
Make sure to click on the Save blocks button when you are done changing the drop-down boxes.
Under this first section, you can override the default block title. If you'd like for no title to be displayed, then enter <none> in this field.
This section controls how much users can control the visibility of a block. You can allow users to show or hide this block as well as specifying the default visibility of the block: shown or hidden.
This section allows you to specify which role can see a particular block. If you'd like to allow all roles to see this block, you can leave this section blank and all users will be able to see it.
In this final section, you can restrict which pages that this block will show up. The radio buttons determine if your list of pages are the pages the block will be displayed on or not. You then put your list of pages in the text area below the pair of radio buttons. Drupal also allows the use of the wildcard '*'. This allows you to specify whole section instead of just individual pages. You can also use <front> to denote your site's home page.
On this page, you can create your own block. The first field is for the block description. This shows up as the block name on the List blocks page. Following that field is a text area allowing you to enter the block body. Click on the Save block button to add this new block to the list.
