This endpoint is commonly used to retrieve metadata of all of the NFTs on a single contract (e.g., Mutant Ape Yacht Club):
Pass a chain and contract address to get back information on the NFTs in this contract
To understand more about the difference between Collections and Contracts, please refer to our FAQ
On Solana, this endpoint will function identically to NFT by Token ID
On Flow, the current list of contracts with metadata can be found here