It’s a record of the blockchain state (ledger) at a specific block height (a specific point in a blockchain). Developers use snapshots to capture receiving wallet balances at a specific time during airdrops. So even if wallet owners pull out their money after a snapshot of their wallet, they can still participate in an airdrop.
IGO
IGO stands for “initial game offering.” It’s an early form of investment that allows the bidders to explore the early development stage of an NFT