What is the difference between standard webservice and wrapped webservice

The difference between wrapped and normal webservice is not very important. The xml files send are very similar in both methodolgy. Than what is the difference.
Difference is about the interfaces:

Standard Document Style Web Service Interface:
public class SimpleServiceSOAPImpl implements SimpleService_PortType{
public String concat(ConcatRequest concatRequest) ... {
return concatRequest.getS1()+concatRequest.getS2();
}
}

Wrapped Document Style Web Service Interface:
public class SimpleServiceSOAPImpl implements SimpleService_PortType{
public String concat(String s1, String s2) ... {
return s1+s2;
}
}

But both are document style web services at real.