This is an example of image post format. You should really set post featured image for image post format or the first image found in post content will be used.
Quote post format also displays post featured image if it's set. This is a demo of free accessibility ready WordPress theme by WebMan Design.Oliver, WebMan Design
Status post format displays the whole content of your post. It is a short status update, similar to a Twitter status update. You can set post featured image or your gravatar will be displayed instead.
This is an example of link post format, which display a whole post content and emphasize the link within. This is an example of link in post content.