insert/edit image popup

Insert/edit image alignment window has an alignment popup: “Baseline, Top, Middle, Bottom, Texttop, absolute middle, absolute bottom, left, right.”

I can find no documentation for what these terms mean (exactly)? They also do not change the formatting of post images in my blog (since my theme only has one CSS designation for images). I’d like to have some more image display options on my blog, and on my feeds … but I can find no information on how to do this using these alignment features. Are they tags that can receive their own CSS designations?

The text seems to always wrap around the image in my blog (which is fine) but I do not want the text to wrap around the image in my feed. Any help would be appreciated.