Nxt bills itself as a "second-generation" cryptocurrency. What this means is that Nxt – and other currencies like it – are less concerned with functioning as a standalone currency and more concerned with providing a decentralized system for online exchange. Nxt comes equipped with a toolkit for creating custom cryptocurrencies that are then secured and tracked in Nxt's ledger. Because this currency was conceived as an online marketplace rather than strictly a form of money, Nxt itself does not have significant retailer acceptance. Most exchanges of Nxt are transacted by individuals and mediated through the software itself.
Nxt's radical innovation is its streamlined cryptocurrency toolkit. New alt coins are cropping up all the time, but many flounder for lack of a strong established network of users. Nxt sidesteps this problem by providing a stable network that can be used to verify transactions of many different types. Cryptocurrencies created and secured in this way can be designed to work in many different ways. For crowdfunding applications, you can design a coin that will only be exchangeable if the funding goal is met. For business promotions, you can issue currency that can only be exchanged with your company, like reward points or air miles. Nxt even offers an option to create shuffleable coins. Shuffling obscures the source and destinations of the coins to increase anonymity.
To reduce overall processing overhead and simplify its architecture, Nxt verifies transactions with a proof-of-stake system by default. This means that the right to record the next block of transactions goes to whoever currently has the biggest stake in the system – that is, the most coins in their account. The richest user doesn't always win, however; coins can only be used after they have been held for a certain amount of time, and coins that are counted towards a user's total have to start accruing that time all over again. For those who prefer the security of a proof-of-work system, Nxt also allows the creation of alt coins that use that method.
Nxt has a reasonably high market capitalization, but this is due in large part to the incredibly large amount of Nxt available. This appears to have been a conscious decision by the designers to shift the currency's focus towards mediating other types of exchange. Still, as a stable currency, Nxt lacks some of the economic soundness of its competitors.
The designers of Nxt have set their sights not just on creating a viable currency, but on fostering an entire fiscal ecosystem online. Nxt has the technology to back up this lofty goal and already boasts a significant user base, but whether it becomes the community of choice for online exchange remains to be seen.