ReactJS is an open-source JavaScript library for building user interfaces. ReactJS web development involves a number of steps, including planning, design, development, testing, and deployment.

During the planning phase, the developer works with the client to define the project requirements, identify the target audience, and determine the project timeline and budget. Once the planning phase is complete, the developer begins designing the web application, typically using wireframes and mockups to create a visual representation of the application's layout and structure.

Once the design is approved, the developer moves on to development, where they write the code that brings the application to life. ReactJS provides a variety of pre-built components and APIs that enable developers to quickly build and customize the application's functionality, such as user authentication, data storage, and server-side communication.

During the development phase, the developer also writes unit tests and conducts continuous integration to ensure that the application is free of bugs and errors. Once the development phase is complete, the application undergoes testing to ensure that it functions as intended.

Finally, the application is deployed to a web server, where it becomes publicly available to users. Ongoing maintenance and updates are typically required to ensure the application remains secure and up-to-date.

Overall, ReactJS web development is a challenging and rewarding process that requires a strong understanding of JavaScript and ReactJS, as well as the ability to develop efficient and scalable web applications. With ReactJS, developers can create powerful, interactive and dynamic web applications that offer an excellent user experience.