Rooting is a process by which you can get root access or administrator priviliges to your Android phone and can flash tweaks, custom ROMs, custom kernels, install additional applications which requires root, use firewall etc. If you don’t what exactly root means, I will suggest you to visit here here.
Root will void your phone’s warranty but it does’nt matter you can get it back!
Rooting Samsung Galaxy Y:
1. Download the zip files to your SD Card (not in any folder).
2. Switch off your phone & boot into recovery mode.
3. Press Vol Up + Power Key + Home button together at the same time to boot in recovery mode.
4. Touch screen is disabled here.
5. Use volume keys for scrolling & home button for selection.
6. Select Apply update for sdcard
7. Select update.zip (which you have downloaded).
8. When it shows Install from sdcard complete written.
9. Select reboot system now.
10. Your phone will restart & first boot may take 5 minutes.
11. Check for an application Superuser and open it.
12. Goto Menu > Preferences > SU Binaries.
13. SU Binaries will update.
14. When it get updated, restart your phone.
You’re done! Your phone is now rooted.
Warning: Do not delete Superuser or you will lose your root!
Unrooting Samsung Galaxy Y:
Follow the same steps (1-10) but in place of selecting update.zip under apply update from sdcardin recovery mode, select update-unroot.zip.