What does “trust certificates signed by this CA” mean?
Trusting a CA certificate means the CA can “trusted” in the future to perform evaluations on certificates that are signed by this CA and determine whether they are valid or not. When creating a new CA, its certificate is never considered trusted on the system by default for security reasons. Trusting a new CA certificate has to be done specifically by the user or administrator. In this case, it can be trusted by clicking “On this machine, trust certificates signed by this CA”.