Registries may reserve domain names - moving them outside the pool of available domain names, without registering them. Anybody searching for the availability status of a reserved domain, gets the result "you cannot register this domain".
Sometimes such a reservation is by laws or policies. "Laws" mostly applies to ccTLDs, for example geographic identifiers or obscene names, "policies" mostly applies to ICANN and/or IANA rules, e.g. the inability to register the domain name "www" or a 2-letter country code.
On the other hand, with the raise of new gTLDs we see many more domains being reserved by registries without legal reasons. Those domains are either reserved for the registry's own use (e.g. the domain name "whois"), or because the registry is unsure about whether or not they will be using it at a later moment themselves, or because the registry just wants to know if there is a market for that domain name.
Domain names in this last category are the most interesting: in many cases we can negotiate with the registry to find a solution to get the domain name. We have done so successfully for brand names but also for generics like "hotel", allowing both registry and registrant to get a price that they deem sufficient.
If you want to register a domain name and see it is reserved, do not hesitate to contact us to see what's possible.