Service request management is the ITIL 4 practice that handles predefined, user-initiated requests for services in a consistent and efficient way. A service request is something a user is entitled to receive: a new starter's account, a laptop, access to an application, a shared mailbox. It is not a disruption and not a complaint; its fulfilment path is known in advance. It is one of the core practices of ITSM, next to incident, problem and change management.
That is what separates it from incident management. An incident is unexpected and needs diagnosis; a request is anticipated and follows a standard workflow with its own SLA. Merging both in one queue is the most common reason request SLAs are missed: incidents get handled like requests, requests wait behind incidents, and neither process performs.