Materialize is a bit more of a lower-level technology, and less of a single "feature". I've included some example use cases built on top of Materialize in my other comment.

In addition, while Materialize does support connecting to other databases, to power "real-time materialized views", a common architecture we are used for is to present a SQL view on top of streaming systems (such as Kafka or Kinesis).

Here's an overview of Materialize that explains the relationship between Timely Dataflow, Differential Dataflow, and Materialize, starting at 23:20 - https://materialize.io/blog-cmudb/