Knowledge of the command line in your operating system will be useful. You will spend most of the time on a code editor and a web browser, but there are some tasks here and there that need to be carried out in a terminal session.
If you are using a Microsoft Windows computer, my recommendation is that you use the Windows Subsystem for Linux (WSL), which provides UNIX-compatible versions of bash, Node.js and all other required packages. Using the Windows command prompt or PowerShell should be possible, but you will need to adjust some command-line instructions.
To test your application as you develop it, you may use your favorite web browser. If you need a recommendation, many React developers prefer Chrome or Firefox, because they are the two browsers that support the React Developer Tools plugin, which can sometimes be useful in debugging React applications.