When creating reports with custom fields, there can be many fields within an account that have similar names that will display as field options. We use the internal name to help differentiate and allow the user to select the right field they are looking for. However, in many cases the choice list options may be different for similarly titled fields. For example, there could be two Priority fields:
Priority (field name) > Global priority choice (internal name) > Options: H/M/L
Priority (field name) > Global priority choice (internal name) > Options: Critical etc.
There is a hover tooltip when working with custom layouts to help preview the options and differentiate, but this is not available to most users who are not customization admins and would like to have this type of preview available with reporting selections.