Most blog theme designs come with widgets that a blogger can use to add custom contents on a blog, notably on the blog’s sidebars. A sidebar is that “narrow” column of a blog, that are either placed on the left side or at the right side.
Depending on the theme’s over-all design, a theme can have a single sidebar and is called a 2-column themes (the layout of this site, Bloggista.net is based on a 2-column theme where the sidebar is placed on the right).
Dual sidebar themes have 3-columns where the sidebars are placed both on the left and right or side-by-side, more popular choice is to place the widgets on the right side (Bloggista.com is an example of a 3-column theme blog).
Some themes could have 4 or more sidebars. However, there are also blog themes that do not have widgets, and the layout is already fixed.
What are the uses of Widgets?
Widgets are used to add customized content on a blog, in the sidebars. In WordPress blogs, several widgets are available that make WordPress a popular blogging platform among bloggers. To use the Widgets, go to YourBlog’s Dashboard > Presentation > Themes | Widgets.
RSS Widgets: Contents can be “feeds” or entries of another blog or site. You can place up to 10 RSS widgets on your blog should you wish.