Javascript invoke function without parentheses [duplicate]

So, I'm very new to Javascript and I've been following this javascript30.com course and it's the first day.

I'm trying to wrap my head around that removeTransition function call. How is that valid and what exactly is getting passed as 'e'?

function removeTransition(e) {
        if (e.propertyName !== "transform") return;
        e.target.classList.remove("playing");
      }

. .

const keys = Array.from(document.querySelectorAll(".key"));
      keys.forEach((key) =>
        key.addEventListener("transitionend", removeTransition)
      );