Most businesses already have an Enterprise PKI or a Public PKI they trust. VMware allows you to configure vCenter in order to leverage certificates from such PKIs. This is achieved by configuring VMCA as an Intermediary CA or Subordinate CA to your Enterprise CA or Public Key Infrastructure (PKI).
Read the following Wikipedia article on PKI to gain a basic understanding: https://en.wikipedia.org/wiki/Public_key_infrastructure.
One of the benefits of doing so is to reduce the management overhead in the renewal of the Machine SSL and Solution Users Certificates. Once a subordinate, VMCA can issues certificates on behalf of the Enterprise CA. The following diagram depicts the approach of using VCMA as a subordinate authority:
Although using VCMA as a subordinate CA is an option, VMware does not recommend doing so. Use the Hybrid...