Different behavior for featured images?

Hi! I used the Adelle them on my wp.com blog. This weekend i transferred to wp.org and applied the same theme. Is it true that the featured image option works totally different? In wp.com the featured image would display full size and i had to enter in as the an image in the post as well.

In wp.org the featured image is entered automatically and in a much smaller size with text spread around it. Is this correct behavior? Or did i somehow accidentally mess something up in the code?