How Bitcoin work ?

The basics for a new user

As a new user, you can get started with Bitcoin without understanding the technical details.
Once you have installed a Bitcoin wallet on your computer or mobile phone, it will generate your first Bitcoin address and you can create new ones whenever you need to.
You can disclose your addresses to your friends so that they can pay you and vice versa.
In fact, using Bitcoin is quite comparable to exchanging emails, except that Bitcoin addresses should only be used once.

The blockchain

The blockchain is a shared, public ledger on which the entire Bitcoin network relies.
All confirmed transactions are included in the blockchain. In this way, Bitcoin wallets can calculate their balances and it is possible to verify that new transactions are spending bitcoins that actually belong to the payment sender.
The integrity and chronological order of the chain of blocks are ensured by cryptographic means.

Private Key

Bitcoin wallets keep a secret information called a private key or seed which is used to sign transactions, providing mathematical proof that they originate from the owner of each wallet.
The signature also prevents any modification of the transaction after it is issued.
All transactions are broadcast between users and usually begin to be confirmed by the network within 10 minutes by a process called mining.

Mining

Mining is a distributed consensus system that is used to confirm pending transactions by including them in the blockchain.
It enforces a chronological order in the blockchain, protects network neutrality, and allows different computers to agree on the state of the system.
To be confirmed, the transactions must be included in a block which must correspond to very strict cryptographic rules which will be verified by the network.
These rules prevent modification of an earlier block as this would invalidate all subsequent blocks.
Mining also induces the equivalent of a competitive lottery which prevents anyone from easily adding blocks consecutively in the blockchain.
This way, no individual can control what is included in the blockchain or replace parts of it to offset their own expenses.