In case you were wondering.... Here is the difference between the image title and the image description - preferably for your AR (Active Rain) posts but useful everywhere images are inserted. Being new to Active Rain I am coming across a lot of details that some bloggers may not know. (and I'm not seeing a lot explanations about) This is one where it may be a bit confusing as to which location to add which tag.
Image Description, also called the <alt> Tag is what Google and other search engines will see because they cannot see images. If you want search engines to "see" your image for what it is, you must add a description to it. This is the image description.
Image Title is what actual visitors will see when they hover over the image. The below image has a TITLE of "This is a picture of a gingerbread house" is for visitors either not seeing the image clearly due to the platform they are viewing it on or for a better description of it. You can also title it "Click here for more pictures of gingerbread houses" and have it hyperlinked to another page. Then visitors will know what they get when they click on it.
The DESCRIPTION of this image that Google and other search engines see is embedded in the code for the <alt> tag "Computer Generated Gingerbread House" so the search engine knows there is an image here with that explanation.
The image description should have your main keywords about the image but not be stuffed with 200 words repeated over and over. Google sees this as stuffing and will sometimes disregard the image altogether.
Your description and title can usually be as long as you want them to be. But a short sentence or 8-20 keywords are typically the best. Its also a great way to add more keywords into a post or article but don't go overboard. The description should include your keywords and your title should be what the image is about for actual visitors. Many times, they can be the same too.