Also update URL List 
Check this box, then click ‘Update
Item Data’. It will update the changes made on this item page to the URL
list of items (found at Import/Exports > Export Item URL list). The URL is
the list of item URLs (links). 

Most of the time you would check this
box is if you changed the name for this particular item, and you want the
item URL list to reflect the new name. URLs automatically change the link to
reflect the new name, so the URL list needs to be updated if you change the
name. For example, if you change the name of your item title from Fishing
Pole to Bob’s Fantastic Fishing Pole, the url would change from
www.yoursite.com/item/Fishing-Pole-10 
www.yoursite.com/item/Bob’s-Fantastic-Fishing-Pole-10 

The URL list is used by the Sitemap page, which is designed to help with
search engine crawling bots.

Google Product Search 
Check this box, then click ‘Update
Item Data’. It will update the changes made on this item page to the Google
Product Search page (found at Promotion > Export Google Product Search) 

This checkbox is designed for when you update one item at a time. If you
currently have a Google Product Feed and are updating this item only, this
is a good box to check. If you are creating a Google Product Feed or
updating a lot of items, please navigate to the Promotion > ‘Export Google
Product Search’ page. At that page you will be able to load/update all items
at once for the Google Shopping feed.

Sitemap page 
Check this box, then click ‘Update Item Data’.
It will update the changes made on this item page to the Sitemap.xml file. 

This option is for the Sitemap.xml file only. You are also able to load an
HTML Sitemap (found at Promotion > Sitemap), which is also helpful for
search engines. This HTML Sitemap is not affected by this checkbox. 

The purpose of the sitemap.xml file is to help search engine crawling bots
find all your shopping cart item pages. Contact us, your shopping cart
hosting provider, to get a sitemap.xml file set up.