What is Smart contract?

A smart contract is a program stored on a blockchain that runs when someone sends it a transaction. It holds its own balance and state, it executes exactly as written, and nobody can pause it or reverse a result unless the code allows for that. Tokens, exchanges, lending markets, NFT collections and prediction markets are all smart contracts; the wallet you use only signs messages that call them.

The name promises more than the thing delivers. A contract is smart in the sense of being automatic, not in the sense of being wise: it enforces its rules whether or not they were the rules anyone intended. Bugs are permanent unless the authors built an upgrade path, and an upgrade path is itself a trust assumption, because whoever holds the upgrade key can change the rules.

Interacting with a contract usually means granting it a permission, most often an approval to spend a token on your behalf. Approvals outlive the transaction they were created for, which is how an old, forgotten approval to a protocol that later gets exploited can drain a wallet years later. Reviewing and revoking approvals is basic hygiene.

For a tracker, contracts are the source of truth for every DeFi position. The balance of a pool share, the debt on a loan and the reward accrued on a stake are all state inside contracts, readable by anyone. TrueHold reads that state to decode positions; it never calls a contract with a transaction, because reading needs no signature.

Before trusting a contract with size, check three things: whether it has been audited and by whom, whether it can be upgraded and by whom, and how long it has held real value without incident. None of those is a guarantee. A verified source on the explorer at least means the code you are reading is the code that runs, which is the minimum for anything holding your money.