Think of your Phantom or Backpack wallet like a password manager. It doesn't actually hold your SOL — your SOL lives on the Solana blockchain in Accounts. Your wallet just holds the secret keys (Signers) that prove those Accounts belong to you.
Imagine a massive multiplayer game where thousands of validators keep a copy of the ledger. If someone tries to submit a fake transaction, validators compare ledgers and reject the forgery. Those validators are Solana's 'nodes'.
Consensus is how validators agree on the truth. Solana uses Proof of History (PoH) combined with Proof of Stake — a cryptographic clock that orders transactions before they're confirmed, making Solana incredibly fast.
On Solana, you pay Compute Units (not gas!) for transaction processing — usually a fraction of a cent. You also pay Rent to keep data Accounts alive on-chain. Solana Programs are designed to be extremely cost-efficient.