Again, this is a very simplified version of the answer but:
Bitcoin is basically a math experiment let loose on the world. At it’s inception there were very few people who cared or had the resources to participate and because of the structure they earned lots of Bitcoin in a (now) very short span of time. {more details on this in the mining section of the site} On May 22nd 2010 someone asked the internet to get him 2 pizzas for the, then, worthless price of 10,000 Bitcoin and someone brought him those 2 pizzas. At that moment Bitcoin gained its first value. Since then people have been using Bitcoin to buy bigger and more regular things. With the political turmoil around the world some people have even turned to Bitcoin to buy food and everyday items. Bitcoin’s lack of political and geographical affiliation has made it an ideal currency for many different groups of people around the world.
Many will say that Bitcoin has no checks and balances, that is untrue. Bitcoin has 1 grand check and balance, the blockchain. Where it is true that no country or entity has the power to edit or move Bitcoin around, the blockchain makes sure that every Bitcoin transaction is accurate and true. The blockchain is the PUBLIC ledger of every single Bitcoin transaction that has ever occurred. Because of this one, integral, part of the Bitcoin structure, it is kept in check by the distributed network of Miners and Wallets at all times.
BitcoinFAQ.info 