At the very least, you will need:

• jqGrid plugin,
  
• jQuery library, version 1.1.4 or later, and
  
• a web browser
  

To manipulate and represent local (static) data – i.e. array data, data stored in an xml file, or data stored in a JSON file – that's all you need.

But the primary purpose of jqGrid is to manipulate and represent dynamic data over the web, and for this you will also need

• a web server (e.g., IIS, Apache, Tomcat),
  
• a database backend (e.g., Postgre SQL, Oracle, MSSQL, MySQL), and
  
• a server-side scripting language (e.g., PHP, ASP)