What is the Mendix Modeler?

The Mendix Modeler serves as the integrated development environment (IDE) specifically designed for building Mendix applications. It provides a comprehensive set of tools and functionalities that enable developers to create, test, and deploy applications with ease. Within the Modeler, developers can visually design user interfaces, manage data models, define business logic, and configure application settings. This environment streamlines the application development process, allowing both technical and non-technical users to collaborate effectively on projects.

The other options describe different aspects of the Mendix ecosystem but do not accurately define what the Mendix Modeler specifically is. For instance, while there are extensions available for integrating third-party tools, that function is not encapsulated by the Modeler itself. Similarly, Mendix applications may be hosted in the cloud, but that describes a separate service rather than the development environment. Lastly, a marketplace for downloading user reviews isn't related to the core functionality of building and managing applications within the Modeler. Thus, identifying it as the integrated development environment is the most accurate characterization of the Mendix Modeler.