TrustRelay is a Software-as-a-Service (SaaS) platform to manage data-sharing between organizations.
More specifically TrustRelay is a data-mesh platform that allows the setup of dataspaces/data-collaboratives to share data between organizations using data-sharing agreements and data stewardship principles.
That was a mouthful, let's split the definition in smaller pieces.
A data-mesh platform is based on a modern, distributed architecture for analytical data management, in simple words, it allows you to query data that may be located in different regions, clouds, technologies and formats.
Dataspaces and Data collaboratives
Dataspaces are a virtual network of organizations and people sharing data for a common purpose.
A more specific form of dataspace is a Data collaborative which, according to GovLab, is a new form of partnership in which data (such as data owned by corporations) or data expertise is made accessible for external parties (such as academics or statistical offices) working in the public interest. If you want to know more about data collaboratives check this article from the GovLab.
They are usually legally-binding agreements drafted, analyzed and negotiated between two or more organizations in order to allow access to a data-consumer by a data-provider. These agreements may be customized or standardized, but they all include a certain level of complexity based on roles and responsibilities of the individuals involved in the context of a ruling-jurisdiction.
According to the GovLab, Data stewards are individuals or teams within data-holding organizations who are empowered to proactively initiate, facilitate and coordinate data collaboratives toward the public interest.