The default Joomla sample data has the words "Welcome to the front page" set as the page title in it's homepage menu item. To remove or edit this text simply navigate to Menus -> MainMenu - > Home -> Page Display Options. In this tab you will see a radio button called Show Page Heading. Simply set this radio button to No to remove the page title.

Above this radio button you will notice a field called Browser Page Title. Use this field if you wish to simply edit the "Welcome to the front page" text.