@nsvsrk :
AEM is built on Sling Framework, thus there are many operations that can be performed via REST API (Services exposed via URLs)
In terms of AEM, cURL is utilizes these REST APIs to update/get information about various resources like pages, assets, packages etc.
The operations are listed here: https://experienceleague.adobe.com/en/docs/experience-manager-65/content/sites/administering/operations/curl#common-operational-aem-curl-commands
One need to append credentials to perform these operations. The credentials are further restricted by the permissions one has on the system.
Its definitely not for attacking the systems, rather performing operations via URLs.