ETL abbreviates Extract Transformation Loading.

You see three terms which are  Extract, Transform, Load and   these three database functions combine and use ETL mechanism pulling the  data from one database to  another database with the help of tools such as Informatica.

So what we understand in here is ETL is Mechanism to perform following three functions.

While testing we transfer data from sources to targets such as Dataware houses, Data Marts. During this process we will load data after cleansing  and transforming using tool such as Informatica. And also ETL is used to convert databases from one format or type to another.

An operating system or OS is a software program that enables the computer hardware  to communicate and operate with the computer software . Without a computer operating system, a computer and software programs would be useless

When computers were first introduced the user interacted with them using a command line interface, which required the user to perform a series of commands in order to interact with the computer and its hardware and software. Today, almost every computer is using a Graphical User Interface (GUI) operating system that is much easier to use and operate.

Operating systems can be classified as follows :

Multi-User         : Allows two or more users to run programs at the same time. Some  operating systems permit hundreds or even thousands of concurrent users.

Multiprocessing  : Supports running a program on more than one CPU.

Multitasking       : Allows more than one program to run concurrently.

Multithreading    : Allows different parts of a single program to run concurrently

$(document).ready(function(){

/* you can start writing code in here.. */

});

The above script runs once DOM Loaded,  even of some of the images are still download.

DOM is the nothing but structure of html includes div, table elements with out asset

$("html, body").animate({ scrollTop: 0 }, 500);

Here in this code html, body are selectors
animate is the function to animate the selector
scrollTop is attribute of animate function with the value ‘o’ which is position to where it has to animate.
500 is speed and esasin of animation