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. Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain.

Bitcoin is unique in that there are a finite number of them: 21 million.

Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services.

As of February 2015, over 100,000 merchants and vendors accepted bitcoin as payment.

Bitcoin is often called the first cryptocurrency, although prior systems existed. Bitcoin is more correctly described as the first decentralized digital currency.

It is the largest of its kind in terms of total market value.

There are many companies that allow you to invest in Bitcoin. Some of these companies are listed below:

Coinbase: Coinbase is a digital asset exchange company headquartered in San Francisco, California. They broker exchanges of Bitcoin (₿), Ethereum (Ξ), Litecoin (Ł) with fiat currencies in 32 countries, and bitcoin transactions and storage in 190 countries worldwide.
Gemini: Gemini is a cryptocurrency exchange and custodian that offers investors access to 26 cryptocurrencies and US dollars. Gemini allows you to securely buy, sell, and store cryptocurrencies like Bitcoin, Ethereum (Ξ), Litecoin (Ł), Dai (DAI), Bitcoin Cash (BCH), and Zcash (ZEC)
Circle: Circle is a peer-to-peer payments technology company.

It was acquired by Goldman Sachs in 2015. The company allows users to hold, send, and receive traditional fiat currencies . Crypto assets such as Bitcoin and Ethereum are also available on Circle’s web app
Robinhood: Robinhood is a commission-free stock trading app that gives you the ability to trade stocks, options, ETFs, and cryptocurrency all in one place. They offer 24/7 customer support.