There are many widget areas to place content. You can extend this further using a plugin such as Widget Logic or Widget Context.

Column Two: All
Appears in any template with a sidebar column.

Column Two: Home
Appears sidebar column of the page set in Settings > Reading > Static > Front Page. (or default posts page if nothing is set)

Column Two: Blog
Appears sidebar column of the page set in Settings > Reading > Static > Posts Page.

Column Two: Single Post
Appears on a single post page

Column Two: Single Page
Appears on a single page template, except the home page.

Column Two: Any Archive Page
When any type of Archive page is being displayed. Category, Tag, Author and Date based pages are all types of Archives.

Column Two: 404 Page
When a page displays after an “HTTP 404: Not Found” error occurs.

Column Two: Logged in User
Appears in the sidebar when a user is logged in.

Posts loop: Above
Appears above the loop of posts.

Posts loop: Below
Appears below the loop of posts

Posts loop: Appear After Nth Post
By default, widget area appears in post loop after the first post, adjust this in theme settings. Perfect for ads, sponsors, etc.

Body: Top
Appears at the top of the main body.

Body: Bottom
Appears at the end of the main body, above the footers.

Footer: Full-Width Above
Main footer, full width above Footer Columns

Footer: Full-Width Below
Main footer, full width below Footer Columns

Footer Column: A
Main footer, position in column A.

Footer Column: B
Main footer, position in column B.

Footer Column: C
Main footer, position in column C.

Footer Column: D
Main footer, position in column D.

Footer bottom: Left
Footer bottom bar, left side. Designed for a text widget. Do not enter a widget title. Check the box to add a paragraph tag.

Footer bottom: Right
Footer bottom bar, right side. Designed for a text widget. Do not enter a widget title. Check the box to add a paragraph tag.