If this checkbox is ticked, this disables HTTPS Certificate verification, allowing any certificate to be accepted as genuine.
WARNING: Enabling this opens up a man-in-the-middle security vulnerability.
If connections to vSphere fail and the details mention
"PKIX path building failed"
and/or
"unable to find valid certification path"
then either
the vSphere host that was connected to is an impostor
(e.g. someone is intercepting your network traffic)
or
your vSphere host uses a certificate that is not trusted by the JVM that is running Jenkins
(e.g. your vSphere host is using a self-signed certificate).
If your vSphere host uses a certificate that is not trusted by the JVM that is running Jenkins
then you should add that certificate to the JVM's list of trusted certificates so that it becomes trusted
(typically using the Java keytool utility).
If (and only if) you are unable to do this (and you accept the risks that this entails) then you could tick this box.
This option is disabled by default.