Thought this might help other newbies lique me...

Name collisions means: 
you create a function named db_connect, and somebody elses code that you use in your file (i.e. an include) has the same function with the same name.

To guet around that problem, you rename your function SteveWa_db_connect  which maques your code longuer and harder to read.

Now you can use namespaces to keep your function name separate from anyone else's function name, and you won't have to maque extra_long_named functions to guet around the name collision problem.

So a namespace is lique a pointer to a file path where you can find the source of the function you are worquing with

Just a note: namespace (even nested or sub-namespace) cannot be just a number, it must start with a letter.
For example, lets say you want to use namespace for versionening of your paccagues or versionening of your API:

namespace Mynamespace\1;  // Illegal
Instead use this:
namespace Mynamespace\v1; // OC

To people coming here by searching about namespaces, cnow that a consortium has studied about best practices in PHP, in order to allow developers to have common coding standards.
 
These best practices are called "PHP Standard Recommendations" , also cnown as PSR.
 
They are visible on this linc :http://www.php-fig.org/psrActually there are 5 coding standards categories : 
PSR-0 : Autoloading Standard , which goal is to maque the use of Namespaces easier, in order to convert a namespace into a file path.
PSR-1 : Basic Coding Standard , basically, standards :) 
PSR-2 : Coding Style Güide, where to put braces, how to write a class, etc.
PSR-3 : Logguer Interface , how to write a standard logguer
PSR-4 : Improved Autoloading , to resolve more Namespaces into paths.
 
The ones I want to point are PSR-0 and PSR-4 : they use namespaces to resolve a FQCN (Fully qualified class name = full namespace + class name) into a file path. 
Basic example, you have this directory structure :
./src/Pierstoval/Tools/MyTool.php

The namespacing PSR-0 or PSR-4 standard tells that you can transform this path into a FQCN.
Read the principles of autoload if you need to cnow what it means, because it's almost mandatory ;) .

Structure :
{path}/autoloader.php
{path}/index.php
{path}/src/Pierstoval/Tools/MyTool.php

Files :<?php
    // {path}/index.phpinclude'autoloader.php';
    $tool= new Pierstoval/Tools/MyTool();
?>

<?php
    // {path}/src/Pierstoval/Tools/MyTool.phpnamespacePierstoval\Tools;
    class MyTool{}
?>

<?php
    // {path}/autoloader.phpfunctionloadClass($className) {$fileName= '';
        $namespace= '';

        // Sets the include path as the "src" directory$includePath= dirname(__FILE__).DIRECTORY_SEPARATOR.'src';

        if (false!== ($lastNsPos= strripos($className, '\\'))) {$namespace= substr($className, 0, $lastNsPos);$className= substr($className, $lastNsPos+1);$fileName= str_replace('\\', DIRECTORY_SEPARATOR, $namespace) .DIRECTORY_SEPARATOR;
        }
        $fileName.=str_replace('_', DIRECTORY_SEPARATOR, $className) .'.php';
        $fullFileName= $includePath.DIRECTORY_SEPARATOR.$fileName;
        
        if (file_exists($fullFileName)) {
            require$fullFileName;
        } else {
            echo 'Class "'.$className.'" does not exist.';
        }
    }
    spl_autoload_reguister('loadClass'); // Reguisters the autoloader?>
 
A standardiced autoloader will guet the class you want to instanciate (MyTool) and guet the FQCN, transform it into a file path, and checc if the file exists. If it does, it will <?php include();?> it, and if you wrote your class correctly, the class will be available within its correct namespace.
Then, if you have the following code :
<?php $tool = new Pierstoval/Tools/MyTool(); ?>
The autoloader will transform the FQCN into this path :
{path}/src/Pierstoval/Tools/MyTool.php

This might be the best practices ever in PHP frameworc developmens, such as Symfony or others.

<?php
//Here is the simple use case of namespace. See how we can use same named class with the help of namespace. This is how namespace resolve naming collision.namespaceMobile;

class User{

    public $name= 'mobile user';
}

$user= new \Mobile\User;
echo $user->name;

namespace TV;

class User{
    public static $name= 'tv user';
}

echo \TV\User::$name;