Subversion have a huge list of features what you can get from here. But i have not enough time to read the big list. So in short, subversion is a system which helps developer to backup and recovery(extreme feature) their code time to time. Tortoise SVN is a good subversioning system for windows. Easy to install and use.
Why we use SVN?
Best and attractive feature what i found is Checkout and Commit. Let me explain more. While i am working in a project i change a number of files in different folder. So when we need to synchronize with server we need to enter individual folder and upload files through FTP. Or whatever it’s local office development when multiple (or even single) developer engage in a single project. For all easy way to do this task is : just enter into project folder (eg. htdocs/my_project) now click SVN->Commit. a list of changed files displayed and you can easily check which files you wish to commit. Moreover, you can put a comment for your change. Someone in other end can easily receive these files by SVN->Checkout. He will notified what changes made by whom. It’s the cool feature and a lot more. So lets try to install and use it first.

First download it from here
How to setup ?

In Windows explorer, make a directory where you would like the SVN repository to be.
Right click on the directory you just created, then scroll to TortoiseSVN > Create Repository here…
You should get the following pop-up window:

Choose the file type you would like and click OK.
How do you know it worked?

You should get the following message:

Import the project into the SVN repository

Go to your work area in Windows Explorer. Right click on the directory you just created, then scroll to TortoiseSVN > Import…

Click on the button in the top right to browse for the location of the SVN repository that you just created. Once selected, add a “/trunk” to the end of the file location. Enter “initial import” in the Import Message field. Click OK

How do you know it worked?

You should get output as follows:

Start using the SVN files in your work directory

To use the SVN repository, we’ll actually want to checkout the files in an empty directory – SVN needs an empty directory to start.

Using Windows Explorer, rename your project directory from aminul_stull to aminul_stuff_backup . Create a new work directory named aminul_stull Right click on the directory you just created, then scroll to TortoiseSVN > SVN Checkout… In the pop-up window verify that the “URL of repository” has the location of the SVN directory that you created; if not, browse and select it. Make sure you have /trunk added to the raw location. Click OK and you should get the following window:

When you go back to windows explorer, you should now see a green check mark next to the directory.
[SVN er Dorwaja Kholna MAMU]

[NOTE: i have STOLEN maximum content of this article over the net;) Don't worry no one blame you if you use it and get benefited ]