Bitcoin is digital cash. More specifically, bitcoin is a decentralized currency and payment network making it a new kind of money.
Bitcoin uses peer to peer technology to operate without a bank or any type of central authority. Transactions are managed and bitcoins are issued collectively by the network. Bitcoin is open source, with its design completely public therefore nobody or entity owns or controls bitcoin yet everyone can take part in bitcoin. Because of its unique properties, bitcoin allows for extremely fast transactions and a myriad of other exciting uses that could not be covered by any previous payment system.
With bitcoin you no longer have to wait for deposits to clear and company's to send you your money. If you deposit and win you can withdraw quickly. Bitcoins can be purchased for dollars, yen, and all other currencies through exchanges, further explained below. Litecoin and ethereum follow a very similar process.
Additionally, due to bitcoin's peer to peer nature it can be sent seamlessly across boundaries and borders enabling everyone to play at Betcoin.
Here is a short video on bitcoin: