Definitions

U-space airspace means a UAS geographical zone designated by Member States, where UAS operations are only allowed to take place with the support of U-space services.
U-space service means a service relying on digital services and automation of functions designed to support safe, secure and efficient access to U-space airspace for a large number of UAS.

Source: Regulation (EU) 2021/664

Concept

U-space is the European system that is being developed to manage UAS (unmanned aerial systems) traffic. It is a set of specific services and procedures designed to ensure safe and efficient access to airspace for UAS. 

The purpose of U-space is to achieve automated UAS management and integration, allowing for a large series of operations, many of them simultaneous. The process is to be integrated with the current ATM system.