embed-inline, embed, full and line are the different viewmode (different types how to include the image = different templates)
1. embed-inline has no break at the end ( i think )
2. embed has a break (<br>) after the image ...
To find out the differences between the viewmode, create a new contentobject an insert the same image in the 4 viewmodes. Then have a look into the html sourcecode.
Inline and embed should correspond to CSS 'inline' and 'block' elements - the two generics are <span> and <div>. Inline images are pretty rare in html.
Using a <br /> to make an inline element into a pseudo block element is a *bad idea* - if you want a block element, use one!