When a domain name is parked, the domain has to be registered. Once registered the domain will be redirected to a page without content or to a parking page provided by the domain provider.
When a domain is redirected, the registered domain is forwarded to a target requested by the client.
From the technical point of view there is no difference between these two terms, it is only the target of the redirection that makes a difference.
Colloquially, a “reservation” of a domain is not possible. A domain registration incurs costs!