What's the difference between using a function with "()" and when we use it without them in Javascript?

function find() {
    console.log("Request handler 'find' was called.");
}
function display() {
    console.log("Request handler 'display' was called.");
}

exports.find = find;
exports.display = display;

1. sometime we call function with parentheses and sometimes we don't use them.

Like in DOM i get why we do no t use it with event Listeners because we want to them to only work when click occurs, But in node like the above example why we didn't used any parentheses?

without the parentheses you are assigning the function itself ( functions are first class objects ) whereas with the parentheses you are executing the function and assigning the resultant value