Mendix is a low-code platform for Rapid Application Development (RAD) that allows developers to create scalable enterprise applications using visual models, reusable components (RUCs), and a model-driven development approach. It combines productivity-focused abstractions with the flexibility to extend applications through custom code, APIs, and integrations.

StackOverflow defines Mendix as
Mendix is a app platform-as-a-service (aPaaS) for Rapid Application Development.
Mendix features:
- version control
- unit testing
- WYSIWYG page building
- LLM agent support
- persistence layer with ERD and entity creation
- microflows, nanoflows and integration with native java actions
- model-driven platform vs. IDE
On this website you can find a comprehensive tradeoff analysis against high-code development platforms like Java + IntelliJ.