Values set in Choice-type column have a Description field.

This field does not seems to be used but could be used in model-driven apps and canvas apps to provide a tooltip explaining what a given choice represents.

This would be useful for fields where a tooltip could guide to new employees to use the appropriate value for a given record.

For example, when select something like a case type or a lead type, if the user is not sure what value to set, they can try a value and hover over the field to see the tooltip to help confirm that they have selected the appropriate type for the record.