Static resources are a new type of storage in Salesforce specifically designed for use in Visualforce pages. They are ways to store images, flash files, stylesheets, and other web resources on the Salesforce servers that can be cached for better page performance.
Static Resources. Static resources allow you to upload content that you can reference in a Visualforce page, including archives (such as . zip and . jar files), images, style sheets, JavaScript, and other files.