Rithmic is a company that develops software, collocates machines near the exchanges’ own servers, and operates a data+order feed that can be offered by brokers to their customers. They are one of the fastest feeds out there, and they provide order routing + real-time data + limited historical data. Some futures traders can use them as their only market connectivity. (If you need longer history for backtesting you’ll need an add-on feed or data supplier.)
I assume that you are asking about R Trader because you saw somewhere that Rithmic has its own platform, but please be aware that you don’t need it to execute via R Trader and use their data feed that we can connect for you.
You can also use the the R Trader platform for free with any platform that uses the Rithmic feed while both connected to the same account.