Javelin is the latest extension to Grid-Tools' Agile Designer, where the latter is the company's product for automating the development of test cases using a flow chart driven approach (derived from requirements) and the former extends that to the automatic generation of tests and the running of those tests. Specifically, Javelin is focused on the automation of what we might call "language independent testing". That is, things such as user interface testing, SOAP and REST calls, flat file testing, message queue testing, ETL (extract, transform and load) testing, and so on. In other words, those elements of an application that are independent of the language being used to develop an application more generally.
Agile Designer (without Javelin) generates test cases based on requirements that are captured in flow charts. This has been described elsewhere and we will not discuss it in detail here (see: The requirements gap: Agile Designer. With Javelin, Agile Designer has been extended to include an automated testing framework. What Grid-Tools calls "active automation" involves automated test case generation, automated script generation and automated execution. It also has automated change capabilities. It relies on a model-driven approach where testing is broken down into logical steps. This makes it much easier to automate each of those steps.