Sunrise and Landrush are two separate periods of time relating to the delegation and launch of a new domain extension (TLD). Both take place before the public launch of a TLD, at which point anyone can register a domain with the new TLD). There are financial or legal considerations for both.
Before a new TLD is released to the general public, some registries offer a sunrise period, which allows brand and trademark owners to register their domains first.
The goal here is to prevent someone from registering a domain like iwantmyname.TLD before we get the chance. This helps prevent trademark violations and other legal issues after the launch, since we, or other companies, have legal rights to certain names.
For more information about sunrise periods, ICANN's TLD Startup Information
After a sunrise period, the landrush period gives people the chance to buy domains before the general public, but usually for a premium cost.
The people or companies who participate in the landrush period don't necessarily have any specific rights to domains with the new TLD, like a trademark. They're just willing to pay extra for a better chance of securing their desired domain name(s).
At iwantmyname we do not participate in sunrise or landrush periods. We do not agree with "pay to play" models for the internet. For new TLDs that we carry we do offer pre-orders before launch, but pre-orders are only processed during the public launch of the TLD, so all customers have the same access to new TLD domains and chance at securing the registration.