Basically, you just need an IDE (Integrated Development Environment) or a text editor, and a host (a place to store your website's files whether that's locally or on a server).
Some good text editors are:
Some good IDEs for web development are:
Codepen.io is a nice place to mess around without hosting a web page. It's also nice to browse other people's projects to get inspiration and see how other people code.
P.S. Google is your friend. Try making a website or a web app and use Google to help you along the way with anything you don't know how to do. It helps wonders to just dive in try to make things work (even if it seems slow sometimes).