By default, on the top left of each SharePoint 2013 site there is a “SharePoint” text. This can be replaced by overriding a delegate control called “SuiteBarBrandingDelegate“. But if you simply want to change the text without writing any code, using 3 line PowerShell script is the easiest way.
$webApp = Get-SPWebApplication http://sharepoint_web_app $webApp.SuiteBarBrandingElementHtml = "Your text" $webApp.Update()
If you want more detail about overriding SuiteBarBrandingDelegate control, follow this link: