Wordpress widgets allow you to customize your blog's sidebars. Depending on what theme you chose dictates the amount of sidebars available and the placement of those sidebars. The most common widgets are the following:

Akismet: A spam filtering plug-in.  To activate you must have your API key found in the settings menu and you must enable the plug-in in the plug-in menu.
Archives:shows your monthly archive of your blog’s post in the side panel.
Calendar: Adds a calendar of your blog’s post to the sidebar
Categories: Adds a list or drop down of your post's category.
Links: Shows the links that you have added to your dashboard account. You can edit these by clicking the Links tab in the left toolbar.
Meta: Adds a menu to your sidebar that includes login/out, admin, feed, and WordPress links.
Pages: Shows all of your WordPress pages in the sidebar.
Recent Posts: Shows your most recent posts in the sidebar.
RSS: Adds an RSS option to the sidebar.
Search: Places a box that allows guests to search through your blog posts.
Text: Allows you to enter text or html content in your sidebars.

With the addition of other plugins you will have more widgets available to use. For instance, with the ecommerce plugin you can add your shopping cart, recent products and other shopping related resources to your sidebars.

Step 5: WordPress Plugins>>