WordPress Widgets add content and features to your Sidebars or other Widget Areas on your site. Widget Areas may vary depending on the theme.
Usually you may see ‘Primary Sidebar’, ‘Archives Sidebar’, ‘Post Sidebar’ or ‘Page Sidebar’, ‘Before Content’ and ‘After Content’ widget areas for your ads, etc.
You can use either standard WordPress widgets, or custom widgets that are built into this theme. Plugins will often add their own widgets.
To place some widgets in widget areas, go to Appearance > Widgets.