Namecoin is an alternative domain name system (DNS) which is based on the Bitcoin software and protocols. It is an open source cryptocurrency that operators on a blockchain network and its key feature is its secure key data storage system, that also acts as a decentralized DNS system for the .bit domain. This means that you can purchase extremely cheap .bit domains by owning Namecoins and you will need to renew the subscription every 250 days in order to maintain it. Nobody else can take over your domain name as long as you keep paying the 0.1 Namecoin fee and your domain will be listed on all DNS that can access the .bit domains. To obtain Namecoins you will either need to mine it through the Namecoin wallet, using the same protocol as the Bitcoin or buy buying the Namecoin on the different cryptocurrency exchange sites online. Since the Namecoin is basically build upon the Bitcoin, it will have a total of 21 million coins that can be mined and once they have been mined they will continue to be in circulation.
The Namecoin was originally not created to go in and become a cryptocurrency that people would be trading, but was made for people who wanted to support a completely anonymous and decentralized DNS system and pay for it completely anonymously as well with the coins. However since people quickly discovered the value in this type of coin, lots of people who were not particularly interested in the coins usage, but rather in the value of it, decided to invest in the coin and sell when it grew in value. This took focus slightly away from the main purpose of the Namecoin, but the people behind has done a good job to promote its actually functionality ever since, which has meant an increase in people interested in the coin for the right purposes holding it now. The Namecoin did however encounter a problem with the domain name registration as a group of people decided to go and register a lot of the best domains as the first, hoping to get good money for the names when people wanted to buy them from them. This issue has yet to be completely resolved, but it is however under control so that it will not continue to happen.
The Namecoin is currently the 8th largest cryptocurrency, which is measured on the market capitalization. There is around 8 million Namecoins in circulation currently and the value of each Namecoin is around $5-$6, giving it a total market value of around $45.5 million. It will not be able to take over most of the other coins position, simply because the market for the coin is too narrow and not something that can be used mainstream like the Bitcoin and Litecoin is for example. The value might go up or down in the future for the Namecoin, it is pretty difficult to predict as it depends on how popular their DNS system is going to be as well as how many of the coins that are currently with speculators trying to make a quick buck of the currency.
As described above, the primary use of the Namecoin is to obtain .bit domain names along with hosting, providing you with completely anonymous domains and hosting. The coins can be used to purchase the available domains and the transactions will be confirmed on the blockchain so you can always prove that you own a domain. Otherwise the Namecoin is a investment coin primarily, which can be used to speculate into increasing or decreasing value and make money that way through on it.