What is SSH? I really did not know the abbreviation until I googled it. It stands for "Secure Shell". To be brief, with SSH connection between RPI and another computer, you can access the terminal prompt of RPI from the other computer (say your PC). Thus you will be able to execute commands remotely for the RPi from your PC without the need for a keyboard and mouse.
What is VNC? Virtual Network Computer. It is just like team viewer or any other remote desktop stuff, with which you can see your RPi's desktop on your PCs screen, enabling GUI based access of RPI.
Assuming that you have an SSH enabled RPI, the tutorial follows.
Make sure that your host PC and RPI are connected to the same network (I mean to the same router) or at the least, you can try a direct ethernet cable connection between the host PC and RPI. This is called peer-to-peer connection.
Now to know the IP address of RPI, use any IP scanning tool like advanced IP scanner
Run the IP scanner and know the IP address of RPI. I have connected RPI and my PC using ethernet cable and the observation is as in Figure 1 of the slideshow below. It shows that the IP address of RPI is 192.168.137.84. This is a vital information now. SO note it down.
Now open Putty to sneak into RPI's terminal and type the address and port number and click open. Refer Fig 2.
Now putty is open and enter the login details. Hurray..! The terminal of RPI is open..!! Refer Fig 3.
Now that we have sneaked into RPI's terminal, we can execute commands on behalf of RPI from our host PC.
The next step is to install VNC server on raspberry pi. Use the commands
sudo apt-get update
sudo apt-get install tightvncserver
in putty's SSH terminal to install VNC server on RPI. It should show whatever that comes up in the terminal of RPI. Once VNC server is installed, you must start the VNC session by typing the command
$ sudo vncserver :1 -geometry 1280x800 -depth 24
where 1280x800 denotes the size of the window in which you want to view RPIs screen on your host PC monitor. If it is for the first time, it will ask you to enter the password for desktop session. Enter any password of your choice and DO REMEMBER THE PASSWORD. follow Fig 4.
Now download any VNC viewer. I am using real VNC viewer for windows. Open the viewer and type in the address of RPI along with the desktop number as seen in Fig 4 as "New X desktop is rajvigneshtn : 1". So the desktop number is 1.
Enter details of IP address of RPI and the desktop number as in Fig 5. If it is giving a warning, just continue and enter the desktop password which you are supposed to remember.
Boom..!! RPI's desktop is now on your PC screen. Happy hacking..!! Fig 6.