Ref - https://solana.com/docs/core/accounts

On Solana, all data is stored in what are referred to as "accounts”. The way data is organized on Solana resembles a key-value store, where each entry in the database is called an "account".

Key points

• Accounts can store up to 10MB of data, which can consist of either executable program code or program state.
  • Programs (smart contracts) are stateless accounts that store executable code.
  • Data accounts are created by programs to store and manage program state.
• Accounts require a rent deposit in SOL, proportional to the amount of data stored, which is fully refundable when the account is closed.
• Every account has a program owner. Only the program that owns an account can modify its data or deduct its lamport balance. However, anyone can increase the balance.
• Native programs are built-in programs included with the Solana runtime.

Account

Each account is identifiable by its unique address, represented as 32 bytes in the format of an Ed25519 PublicKey. You can think of the address as the unique identifier for the account.

AccountInfo

Accounts have a max size of 10MB (10 Mega Bytes) and the data stored on every account on Solana has the following structure known as the AccountInfo.

<aside> 💡

Even if you store not data, you have to store fields like executable and owner which is why you still have to have a minimum amount of SOL as rent solana rent 0

</aside>

Example accounts

• Account with no data (Owner - SystemProgram)
• Account with some data (Owner - TokenProgram)
• Program account (Owner - BPF Loader)