A sidebar is a column on your page(s) that is positioned to the left or right of your main content area, and is usually narrower than the content column. Sidebars usually contain widget areas, although some themes have built in sidebars that are decorative and do not support widgets.

Sidebars are usually included in the column count of a theme (so a two-column theme would have one sidebar and a content column). The number and locations of your sidebars is determined by your theme.

A fixed sidebar is a sidebar that displays the same content in the same position even when you page down in your main content.

Some theme authors may also use the word “sidebar” to refer to widget areas that are in the header or footer.