Go to URL configuration in Settings Option.
Profiles and Profiles Aliases are related to core URLs.
Configurations to plugin URLs (mainly set in e_ulr addon)
Settings are related to all site behaviors.
- it replaces legacy URLs with pretty URLs
Just select the preferred option.
It is something like taxonomy slug in Wordpress. You can set the different alias (slug) for each e107 part of the core and you can them differently for each language.
Overview of all available e_url addons.
If there is an option to change the alias, then alias name is editable.
Remove file name from URL - not clear
Associate Root namespace - if you select page, then page alias is removed from URLs
Warning: you get 404 look/result for page, not system 404 page
Redirect to System not found page - error.php is displayed directly, not pretty URL. It doesn't work with page root.
SEF string creation type - the most important setting. It uses for generating SEF URL (slug) from for example title. In Admin UI (custom plugin) you can set the source for generating slug.