ERC-1155 allows a single contract to manage many token IDs at once, where each ID can have a supply of one, like an nft, or millions, like an erc-20. Batch operations move several IDs in one transaction.
Games and large collections use it because deploying and transferring is far cheaper. Editions with a fixed supply of, say, 500 copies fit the model naturally.
Example: sending 12 different item types costs one batch transfer instead of 12 separate ones, which on a busy chain is the difference between a few dollars and tens of dollars of gas-fee. The diligence questions are identical to any other token contract.