What does it mean by client in the software design patterns?

What does it mean by client in the software design patterns? For instance I see this word has been mentioned a lot in design patterns, such as in this PHP Visitor Design Pattern tutorial. It even has a class called Client.

//Client.php
error_reporting(E_ALL | E_STRICT);
ini_set("display_errors", 1);
// Autoload given function name.
function includeAll($className)
{
    include_once($className . '.php');
}
//Register
spl_autoload_register('includeAll');

class Client
{
    private static $shapeElement;
    private static $color;
    private static $package;

    //client request
    public static function request()
    {
      self::$shapeElement= array();
      self::$shapeElement=$_POST['shape'];
      self::$color=$_POST['color'];
      self::$package= array();

      $obStructure = new ObjectStructure();
      $colorVisitor= new self::$color();

      //Attach concrete elements to array & accept visitor
      foreach (self::$shapeElement as $shapeNow)
      {
        $obStructure->attach(new $shapeNow,$colorVisitor);
      }

      //Display selected shapes
      self::$package=$obStructure->getElements();
      foreach (self::$package as $colorShape)
      {
        echo $colorShape->showShape();
      }
    } 
}
Client::request();

From wikipedia, the client in client–server relationship, which is what I usually understand it as,

A client is a piece of computer hardware or software that accesses a service made available by a server. The server is often (but not always) on another computer system, in which case the client accesses the service by way of a network. The term applies to programs or devices that are part of a client–server model.

Is this then the definition for client in the software design patterns as well?

If the client is made into a class,

class Client
{
    ... 
}

then, can I have many clients as well and where should I keep these clients in MVC architectural pattern? Should/ can I create a directory called client and keep all client classes in it?