Namecoin is an experimental open-source cryptocurrency which is even more decentralized, secure, uncensored and private. Namecoin's code is almost identical to Bitcoin's. Namecoin is the basis for decentralized domain name systems (DNS), i.e. web URLs, that could end Internet censorship.
A DNS system means that top-level domains are independent and DNS lookup tables can be accessed within a peer-to-peer system. As long as there are people running DNS server software, others can access alternative domains. Besides physically getting rid of such servers, authorities have no other way of affecting peer-to-peer top-level domains' well-being.
Bitcoin is a peer-to-peer system whose participants are continuously validating a series of transactions without any central authority. Initially, the idea behind Namecoin was to directly insert data into bitcoin's blockchain. But it was altered later on: bitcoin's protocol was modified, thus creating a separate blockchain. This is why Namecoin and Bitcoin do not interact or interfere with one another, despite the fact that they are almost identical.
Namecoin supports several transaction types. 50 coins are generated for each solved block of crypto problems. The pool of namecoins is capped at 21 million.