The extended form will put an extended part of the article on an additional page, for long articles or articles with multiple pics.
Use <a href="url" target="_blank">*Link Title*</a> for links and put <p><b>Source:</b> <a href="url" target="_blank">*Link Title*</a> after your post to link to your source if you got the information off the net - it will look and act like this when done correctly: Source:Sonic HQ.