Semantic Web
The web where semantic content has been included in web pages to make the web machine-understandable. Then Inference based services can add value to the ecosystem by generating new konwledge.
We can use something like XML to annotate web pages. However even XML is only parsable but there is no understanding or actual knowledge of the data in it.
The current web
Made up of resources that are identified by untyped URIs and connected via non-descriptive links. A machine would have to be able to get knowledge from the context around a link.