Yes. Juicebox allows each image to have a unique title and caption, both of which are displayed in the caption area within the gallery.
The position of the caption area is determined by the captionPosition configuration option.
Please see the description of captionPosition on the Config Options page for a list of possible values.
To have the caption area displayed below the main image in the gallery, you would set captionPosition="BELOW_IMAGE" (in JuiceboxBuilder-Pro's 'Customize -> Caption' section)

If you are creating a gallery with JuiceboxBuilder-Pro, then you can enter the image title and image caption on the 'Images' tab. Just click a thumbnail image to reveal its title and caption input fields.
Otherwise, you could manually add/edit titles and captions directly in your gallery's XML file in a text editor. If doing so, then you might find the Manually Creating a Gallery instructions useful.

A title and/or caption can be as long as you like (within reason) and you can make the text multi-line by using HTML line breaks (<br>). Please see this FAQ for more information about using HTML formatting within image titles and captions:
How do I add HTML formatting to image captions and titles?

If you have a long title/caption, then, depending on the captionPosition, you might need to increase the maxCaptionHeight (in JuiceboxBuilder-Pro's 'Customize -> Caption' section) in order for all the text to be visible.

I hope this helps.