Tell about call stack: how it works, in what order tasks are executed.

Call stack is a data structure used to manage the execution of functions in JavaScript and other programming languages. When a function is called, it is placed on the call stack. After the function completes, it is removed from the stack, and control returns to the previous function.

Sequence of operation:

1. When a function is called, a new frame (execution context) is created and placed on top of the stack.
2. The function's code is executed.
3. If another function is called inside the current function, it is added on top of the stack.
4. When the function finishes, its frame is removed from the stack.
5. Control returns to the function that was called earlier.

This ensures the order of function execution — the last called function executes first (LIFO).

Example:

function first() {
  second();
  console.log('first');
}

function second() {
  console.log('second');
}

first();

Calling first() is placed on the stack, then inside it second() is called, which is placed on top. After second() finishes, it is removed from the stack, and execution of first() continues.