The title attribute displays when you hover over an image, this appears in a tooltip. The image title is often referred to as the 'Title Tag' even though it is not actually a tag.

Ensure your images titles are succinct and descriptive. This will benefit your visitors, though it will also assist your CMS users to quickly locate the image when browsing images within the CMS.

In considering SEO, try not to be spammy. Aim for under 50 characters, though absolutely no more than 70 characters.