EMET is an outdated tool that was used to complement local AV programs. It was last updated in 2016 and is no longer required. I don't believe it serves a useful function anymore.

Here is Microsoft's description of the utility:

The Enhanced Mitigation Experience Toolkit (EMET) is a utility that helps prevent vulnerabilities in software from being successfully exploited. EMET achieves this goal by using security mitigation technologies. These technologies function as special protections and obstacles that an exploit author must defeat to exploit software vulnerabilities. These security mitigation technologies do not guarantee that vulnerabilities cannot be exploited. However, they work to make exploitation as difficult as possible to perform.

EMET also provides a configurable SSL/TLS certificate pinning feature that is called Certificate Trust. This feature is intended to detect (and stop, with EMET 5.0) man-in-the-middle attacks that are leveraging the public key infrastructure (PKI).