The Universal Query System (UQS) is a system for undertaking spatial queries in a 3D world. In a nutshell, the UQS is used to query items, rank and filter them and then return the best 'N' resulting items.
The UQS entity component, on the other hand, works in the background and makes use of the functions and signals that have been set up in a Schematyc graph.
For more information about the UQS, please refer to the Universal Query System (UQS) reference page.