How to find out which NVIDIA GPU I have

If you have it installed, you can also use nvidia-smi which provides even more information for NVIDIA GPUs (this is, after all, what they use in the page you linked):

$ nvidia-smi

Mon Sep 15 16:02:31 2014       
+------------------------------------------------------+                       
| NVIDIA-SMI 340.32     Driver Version: 340.32         |                       
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|===============================+======================+======================|
|   0  GeForce GT 650M     Off  | 0000:01:00.0     N/A |                  N/A |
| N/A   59C    P0    N/A /  N/A |      8MiB /  2047MiB |     N/A      Default |
+-------------------------------+----------------------+----------------------+

+-----------------------------------------------------------------------------+
| Compute processes:                                               GPU Memory |
|  GPU       PID  Process name                                     Usage      |
|=============================================================================|
|    0            Not Supported                                               |
+-----------------------------------------------------------------------------+

If you just want the GPU name:

$ nvidia-smi --query-gpu=name --format=csv,noheader
GeForce GT 650M

please update your PCI ID database with:

sudo update-pciids

And use the following command in your terminal:

lspci -nn | grep '\[03'

You will see the model name of your graphic card. If it's ambiguous, you could search the PCI ID (something like [10de:11bc]) on the Internet for the corrent model name.

Most can be found out by using the lspci command in conjunction with grep.

Most GPU's are listed with model name with the following command:

lspci | grep VGA