Generics vs interfaces? What does it get me?

generics.cs

public interface IFoo { }

public class Something<TFoo> 
  where TFoo : IFoo
{
  public void DoSomething(TFoo foo)
  {
  }
}

interface.cs

public interface IFoo { }

public class Something
{
  public void DoSomething(IFoo foo)
  {
  }
}