Selenium Standalone Server - is a java jar file which is used for starting selenium server which is as word say server, proxy to selenium grid for browsers you want to automate.
The server is good for several reasons:
- Test distribution over the remote machine, or multiple machines (nodes),
- Test on different browsers with different versions,
- Test that is not developed using the Java bindings (i.e. Python, C#, or Ruby) and would like to use HtmlUnit Driver
Client jar can also be acquired by tools like maven or Gradle, open-source build automation systems.
<!-- https://mvnrepository.com/artifact/io.appium/java-client -->