Secure forms are used when you need an agent to collect some information from a customer, but wish to do so in a secure manner and do not wish to save this information. A good example would be credit card information for a one-time payment, or some personal identifying information validating the visitor is who they claim to be.
First you will need to create a form for your agents to use. The Secure Forms are created in the Design section. If you do not see the option, it may not be active in your account. Contact firstname.lastname@example.org and ask for your Account Manager to contact you regarding adding this feature.