Explanation:

VoLTE stands for voice over Long Term Evolution. VoLTE is an Internet Protocol Multimedia Subsystem (IMS) specification which enables a variety of services to operate seamlessly on the network rather than having to switch to different applications for voice or video.
VoLTE is a technology update to the LTE protocol used by mobile phone networks. Under LTE, the infrastructure of telecom players only allows transmission of data while voice calls are routed to
their older 2G or 3G networks.

This is why, under LTE, one cannot access 4G data services while on a call. This leads to problems such as slow internet speeds and poor voice clarity.
VoLTE allows voice calls to be ‘packaged’ and carried through LTE networks. This would mean 4G data accessibility even during calls.
Benefits of VoLTE:

VoLTE provides a more efficient use of spectrum than traditional voice and increases handset battery life.

VoLTE ensures that video services are fully interoperable across the operator community, just as voice services are, as demand for video calls grows