What is the Static Resources in Salesforce ?

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.

Using a static resource is preferable to uploading a file to the Documents tab because:

You can package a collection of related files into a directory hierarchy and upload that hierarchy as a .zip or .jar archive.
You can reference a static resource in page markup by name using the $Resource global variable instead of hard-coding document IDs:

Static assets permit you to transfer content that you can reference in a Visualforce page, including documents, (for example, .compress and .container records), pictures, templates, JavaScript, and different documents.

Utilizing a static asset is desirable over transferring a record to the Documents tab in light of the fact that:

You can bundle an assortment of related documents into an index chain of command and transfer that order as a .zip or .container file.

You can reference a static asset in page markup by name utilizing the $Resource worldwide variable rather than hard-coding report IDs: