In WebCP you can select Parked Redirection to either No Redirect or Redirect to Parent.
No Redirect: In this mode there is no redirect. If your parent domain is example.com and you park parked.com on top of it then both domains will work with no redirection.
Redirect to Parent: In this mode a redirect to the parent domain is enforced. This means that if a visitor visits http://parked.com then they will automatically be 301 redirected to http://example.com.