That's a tutorial (though it looks like someone posted a question as a tutorial). In theory, you can put commonly used content in them, thus not needing to write the same thing over and over again. Sort of like a sticky, but can be embedded in a post. If it's selected as a solution, both you and the author get credit.
Need to find that post and convert it to a question...
EDIT: Sorted. Now a typical forum post, though it's on the stale side.
In future, to remove them, hit the edit button. Below the edit window should be the tutorial with a cross at the top right. Click the cross, then hit Update.
To add them, use the 'Add a solution' drop-down below the post box. It only shows tutorials relevant to the current tags, so you may need...