What is the difference between export photos and export unmodified photos

The unmodified originals are the full sized image files that were imported into the library initially.

The Export Photos will give you the edited version (if it's been edited). Also you'll have a chance to change the file size (Mbs) and/or the image size (pixels) during the export and to change the format to jpeg, tiff or png.

Simple

Export the unmodified original exports the unmodified original - exactly what you imported with no modifications of any sort

Exporting the current photos exports what you have in Photos with all modifications included if you chose the options to include the metadata changes

LN

When I export will the location data be saved?

• When you export "Unmodified Original...", the location data can be saved in a XMP sidecar file. Some applications can read these files and apply the metadata to the files on import.
• Exporting the edited versions as "Export Photos... " can include all metadata, if you enable the checkmarks "Include location information" and "include titles, ...".