Part 2/12:
In its simplest form, a node is a program running on your computer or dedicated hardware that maintains a copy of the entire bitcoin transaction history—the ledger or blockchain. Think of it as your personal "bank database," but instead of trusting a central authority, you verify and confirm every transaction yourself.
The analogy provided in the conversation compares a node to a debit card system: the debit card acts as a proxy to the bank's central database, which keeps track of everyone's money and transactions. Bitcoin's special feature is that everyone can run and verify their own copy of this database, removing the need for trusting centralized third parties.