Bitcoin
Bitcoin is a decentralized digital currency, without a central bank or single administrator, that can be sent from user to user on the peer-to-peer bitcoin network without the need for intermediaries.
If the concept of Bitcoin confuses you, check this video out! I also recommend reading about decentralised networks, blockchain and crypto trading to understand the subject in a deeper manner.
Read this article to learn how you can use your bitcoin to buy goods from online stores.