Let's say you've inherited a theme from a client that some other developer made a long time ago, and your job is to update the code and figure out what stays and what doesn't.
Occassionally WC will update its core template library and this will get out of sync with any overrides in a given theme's /woocommerce/ folder. WC will send an alert in the WP backend that various templates are out of date and need updating. The theme will need its override files updated.
(Version examples for this demo: 2.1.1 is old, 3.0.0 is latest)
Go to https://xxxxxxx.zzz/wp-admin/admin.php?page=wc-status and scroll to Templates to see what files are problematic.