Global Router fix the website in a particular URL. We use it for any urgent situation to show a singe page to user. Global Router Page saved in below location:
/development/definition/uri_manager/global_router.xml
See below example:
<URIManager>
<globalrouter>
<controller>home</controller> <!-- Controller Name -->
<action>index</action> <!-- Action Method Name< -->
</globalrouter>
</URIManager>
To enable Global routing we have to active it form admin panel in below location:
Login Admin Panel > Preference > Configuration > Global Router