How does a parameter become a function call in JavaScript? [duplicate]

I often like to say that JS is not my home language and that’s led me to this question.

import Dropzone from "dropzone";

let myDropzone = Dropzone({
  paramName: "file", // The name that will be used to transfer the file
  maxFilesize: 2, // MB
  accept: function(file, done) {
    if (file.name == "justinbieber.jpg") {
      done("Naha, you don't.");
    }
    else { done(); }
  }
});

The preceding code is from Dropzone website about their great file upload tool.

The else done() confuses me. How would you know that’s a function if you were calling this? Done sports appears to be a parameter to me. If I’m using a good IDE, would I be directed as such? If not how do I know?