What are cliques? What is Vdisk and how it will communicate with physical data storage at the time of data retrieval through AMP?

A clique is a set of Teradata nodes that share a common set of disk arrays. Cabling a subset of nodes to the same disk arrays creates a clique.
Each AMP vproc must have access to an array controller, which in turn accesses the physical disks. AMP vprocs are associated with one or more ranks (or mirrored pairs) of data. The total disk space associated with an AMP is called a vdisk. A vdisk may have up to three ranks. Hence Vdisk will communicate with physical storage through array controllers.