Blueprints are the attributes defined for the Virtual Machines to be provisioned and how it is to be provisioned and its policy/management settings. A machine blueprint is a complete specification for a virtual, cloud, or physical machine that defines resources, attributes, policies, and method of provisioning for the new system.
These are the options for the blueprints that can be created, first three are self explanatory, the fourth one which is Multi-machine management is a new feature in vCAC 6.0 release.
As per VMware, "A multimachine service is a compound service that is composed of multiple machines, but provisioned and managed as a single entity. The most common example is a multitier application consisting of Web, application, and database servers that interact to deliver a common service or application. A multimachine service can be any combination of virtual, physical, or public cloud machines that need to be provisioned and managed as a single entity."