Disclosure: I work at Kong.

The simplest way to think of Kong is as a piece of software that controls traffic going in and out of an API. At its simplest form, it helps make sure that traffic gets to the right API, is secure, etc.

Where Kong really differentiates itself is its ability to support decentralized software architecture patterns like microservices, service mesh, etc as well as traditional monoliths, regardless of the underlying platform or hardware. Microservices make deploying software a lot faster, and we're the connective tissue that lets those microservices work together smoothly and with older legacy systems.

Kong is indesed open source. We also have an enterprise version that adds a lot of features that make managing kong in an enterprise much easier.