In programming, pass by value and pass by reference are two different approaches to parameter passing when invoking functions or methods. These concepts refer to how the values of arguments are assigned to parameters in function calls. 1. Pass by Value: In pass by value, a copy of the value of the argument is passed to the function or method. Any changes made to the parameter within the function do not affect the original argument outside the function. This means that the function works with its own separate copy of the value. Example of pass by value in JavaScript: 

function increment(value) {
  value = value + 1;
  console.log('Inside function:', value);
}

let num = 5;
increment(num);
console.log('Outside function:', num);
Output: 

Inside function: 6
Outside function: 5
In this example, the `increment` function takes an argument `value` and increments it by 1. However, the increment operation only affects the local copy of `value` within the function. The original value of `num` outside the function remains unchanged. 2. Pass by Reference: In pass by reference, a reference to the memory location of the argument is passed to the function or method. This means that changes made to the parameter within the function affect the original argument outside the function since they are pointing to the same memory location. Example of pass by reference in JavaScript: 

function changeName(obj) {
  obj.name = 'John';
  console.log('Inside function:', obj);
}

let person = { name: 'Alice' };
changeName(person);
console.log('Outside function:', person);
Output: 

Inside function: { name: 'John' }
Outside function: { name: 'John' }
In this example, the `changeName` function takes an argument `obj` which is an object. It modifies the `name` property of the object to `'John'`. Since the parameter `obj` holds a reference to the same object as `person`, the change made inside the function is reflected outside as well. It's important to note that JavaScript is always pass by value, but when dealing with objects and arrays, the values being passed are references to the objects or arrays. So, in practical terms, the behavior may resemble pass by reference. In summary, the main difference between pass by value and pass by reference is that in pass by value, a copy of the value is passed, while in pass by reference, a reference to the original value is passed. Pass by value does not affect the original value outside the function, while pass by reference allows modifications to affect the original value outside the function.