Welcome to the tools part. Tools are programs written for very specific purposes.

Some tools are Java tools. In the past it was possible to run them by clicking on a "Start" button direct from the website. But that made a lot of problems over the years, so now you must download the appropriate "jarfile" and run the application in a terminal with "java -jar /path/to/jarfile". This seems a bit more complex, but eliminates storage of uneccesary many "*.jnlp" files. Additionally you can use the application without a browser and avaiod problems with certification settings. If a tool breaks it can mean, that the memory for the "Java Virtual Machine" is not enought, then you may add a parameter like "-Xmx1024m" to the command.