Are functions passed as parameters always callbacks? JavaScript -

if have code below, pass 2 functions parameters function sayhi, example of callback?

i notice there 2 ways of running these 'parameter functions': either below, call functions defined (as arguments), or alternatively call parameter in sayhi function. difference between callback , anonymous function?

function sayhi(name, testfortrue) {     if (testfortrue == true) {         console.log(name);     } }  sayhi(function() {     return 'zach' }(), function() {     return true; }()); 

another way same result, below. in case evaluating functions @ different time? there practical difference between two?

function sayhi(name, testfortrue) {     if (testfortrue() == true) {         console.log(name());     } }  sayhi(function() {     return 'zach' }, function() {     return true; }); 

yes, functions passed parameters callbacks, if intention function called synchronously (c.f. array.prototype.map) rather asynchronously (c.f. window.settimeout).

in first code block aren't of course passing functions. have 2 immediately invoked function expressions, key part in context immediately invoked. function expressions called @ point appear in code , results of expressions passed sayhi.