It is a digital wallet to store, send and receive bitcoin. Instead of storing your money as a real world wallet does, it saves your public and private keys which in turn helps you send and receive money.
Public and Private Keys?
Take a vending machine as an example, anyone can put their money inside the machine, but they can’t take out the money because they don’t have the key. The only person who can take out the money is the owner of the machine who has the key. The vending machine is the public address which anyone uses to send money to you. You are the machine owner, and the key that he is carrying is your private key. Using this private key only you can access your money and do what you please with it.The public key is the address that anyone can use to send you the money, while the private key is what you will use to send money to anyone else. Remember, ONLY you should know what your private key is, otherwise anyone can use your wallet to send your money to any other addresses.