A node is a logical grouping of managed servers.A node usually corresponds to a logical or physical computer system with a distinct IP host address. Where as a Cell is logical grouping of multiple nodes.
Cell profile : Use the cell profile to make applications available to the Internet or to an intranet under the management of the deployment manager.
Creation of a cell profile generates a deployment manager profile and a federated node profile in one iteration through the Profile Management tool. The result is a fully functional cell on a given system.

Important Terms in WAS
Cell : Represents a logical grouping of multiple nodes for administrative purposes.
Node : Represents a physical system running one or more WebSphere servers.
Server : Represents an instance of a Java™ virtual machine (JVM).
Cluster : Represents a logical grouping of multiple application servers within a cell for administration, application deployment, load balancing, and failover purposes.
Federation :The process of joining a stand-alone WebSphere node to a WebSphere cell.
Picture to visualize the things :
References : [1][2][3][4]

Many people have asked me how to understand the output of df command.
For all of them i suggest strongly one thing try to use df command as like below first
df -h
tvt2086:/products/WAS64ZLX # df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/dasda1           4.2G  3.8G  347M  92% /
udev                   1001M  140K 1001M   1% /dev
/dev/dasdf1           1.3G   14M  1.2G   2% /tools
/dev/mapper/pvols-lhome
                            2.0G   33M  2.0G   2% /home
/dev/mapper/pvols-products
                            6.2G   79M  6.1G   2% /products
/dev/mapper/pvols-ltmp
                            1.0G   33M  992M   4% /tmp

Basically df -h will gives the output in human readable form (-h)
So I will try to explain each column
column 1 : Filesystem
It basically tells how many disk drives are connected and available to the user.In the above case there are 6 drives connected. and they mapped to different folders. Ex : /dev/mapper/pvols-lhome is mounted to directory /home

Column 2 : Size
This basically tells how much capacity the disk is having. Say /dev/mapper/pvols-lhome is mounted to directory /home is of 2 GB capacity

Column 3 : Used
Simple it tells how much is used from the available

Column 4 : Avail
It tells how much is free presently, which is available space

Column 5: Use%
Used disk space in terms of %

Column 6 : Mounted on
This the directory on which the disk is mounted and through which we can use the space available.

we can use df -k Which gives the output in KB format.
Go to any of ur desired location and run the command "df -h ." or "df -k ."
tvt2086:/opt/DCD_Installers # df -h .
Filesystem            Size  Used Avail Use% Mounted on
/dev/dasda1           4.2G  3.9G  308M  93% /

So it tells the disk details from which current directory is taking space.

"du -sh ." tell the space that was being occupied by current directory.
tvt2086:/opt/DCD_Installers # du -sh .
472M    .
In the above example the directory named "DCD_Installers" is occupying around 472 MB on the disk space.

We can get to know more about our system processor details like Brand,model and its speed etc.
That to when we are in windows OS we can just run regedit from start -> run.
Once registry editor launched,
 Navigate to the system key
HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\CentralProcessor\0
It will show many details related to our processor.
Ref : [1]

In some situation after uninstalling the products also the services created by the product will be still in the windows services list.
So it is good to delete those services after cleaning the machine.
To do so the following are the steps.

Method 1 :

Start -> Run -> type Cmd -> Hit Enter
in command prompt
Type sc delete <servicename>
ex :
sc delete IBMWebsphere

Then don'r forget to reboot the system.
Note : To create a new service
sc create <service name>

Method 2 :(Registry clean)
If you prefer to work in the registry rather than through the command prompt to delete services;

    * Click Start | Run and type regedit in the Open: line. Click OK.
    * Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    * Scroll down the left pane, locate the service name, right click it and select Delete.
    * Reboot the system

adduser -u 0 -o -g 0 -G 0,1,2,3,4,6,10 -M root2

adduser  : Command to create a user in linuc
-u           : Set the value of user id to 0 which is generally root user id.
-o            : Set the value of user id to 0 which is generally root user id.
-g           :  Set the initial group number to to 0 generally root user group
-G           : Supplementary groups 0=root, 1=bin, 2= daemon, 3 = sys, 4= adm, 6=disk, 10 = wheel
-M          :  User home directory will not be created