A source is a place or person from which you can obtain something useful or valuable.
A resource is something that can be used to perform some function.
The computer store is a source from which I can buy a laptop.
Once I have the laptop, it is a resource.
Another example would be paint brushes when you are painting a picture. They are a resource, not a source.
Many times, a source is the same as a resource, but not always.