In the real life, we interact and do business with one another. All the business and trade transactions are recorded somewhere whether it's bookkeeping or other forms. This record is for the most part hidden or inaccessible to the public. eg. You don't see the transactions of your friends bank account. We put our trust in banks and other trusted third parties and allow them keep track of verification and validations of these transactions.

Bitcoin uses computers that are networked through the internet, to keep track of collection of data, exactly what banks and other trusted third parties for example do. The collection of data is open to the public and not in control of anyone, not the government, no one. It is public in something called a ledger availabe to every computer on the bitcoin network. This ledger(record keeping) is called the blockchain. Same thing as in the real world, but public, accessible and not in control of anyone.