I guess you mean text in polaroid gallery. When you enable this settings you can select which exactly text element of the gallery image you wish to use as source for the content panel below thumbnails. Actually some styles you can customize directly in gallery admin settings, but some additional customization possible in CSS settings.
If you wish to customize text labels right on hovered gallery thumbnails you can use Interface settings. Please use settings blocks: Image Title text styling and Image Description text styling for customization titles and description of the images. With this gallery settings you can change style of the fonts, size , line size and color of the static and hovered labels.
Our gallery provide you different set of settings for static and hovered title and description.
