magento-module/Block/Display.php

<?php

namespace Retailcrm\Retailcrm\Block;

class Display extends \Magento\Framework\View\Element\Template
{
    public function __construct(\Magento\Framework\View\Element\Template\Context $context)
    {
        parent::__construct($context);
    }

    public function sayHello()
    {
	return __('Hello World');	
    }
}