How to invoke a keystroke in a specific website using Java

I am developing a program to automatically carry out a certain sequence of different key presses on a website, however I don't think this could be done using traditional java, or if it could, can someone tell me how to do it. I've heard of something called Selenium, but I am not sure what that is, or how to operate it, so any help in that department would be more than appreciated. I am aware of the Robot class, but that only affects my IDE, namely IntelliJ. I want to expand the key presses to the point that I can manipulate websites. Thank you in advance