What's the difference between a Resource and an Embedded Resource in a C# application?

“Resource” and “Content” build actions are to access the WPF resources using the Uris. However “Embedded Resource” is for prior technologies. However both options embed the resource in assembly but “Resource” option to be used for WPF.

MSDN provides full explanation here.

A WPF resource (build action = Resource) leverages embedded resources as supported by the core .NET framework, but adds support for accessing the embedded resource via a pack URI. From MSDN:

WPF resource files are not the same as the embedded or linked type of resources that can be configured using the core .NET Framework support for assembly resources. While WPF resource files do leverage the core .NET Framework embedded resource support, the ability to access WPF resource files using pack URIs is easier than using namespaces.

As reported by MSDN,

Embedded resources are the best choice if you have to share application resource (.resx) files between multiple projects. For example, if you have a common resource file that contains your company's logos, trademark information, and such, using embedded resources means you have to copy only the .resx file and not the associated resource data files.

You cannot edit embedded resources directly. If you try to edit an embedded resource, you will receive a message prompting you to convert the item to a linked resource in order to edit it. Conversion is recommended but optional. You must export them, make your modifications in an external program, and then import them back into your project.