Bitcoin is two things. It is a currency when written with a small “b” and a network when an upper case “B” is used.
As a currency, it is a store of value, something that can be exchanged for goods and services, like dollars or Euros, but it exists only in digital form.
The Bitcoin network is best thought of as a payment system like Visa or Mastercard. Bitcoin, however, uses a different form or recordkeeping, a series of blocks of information known as a blockchain