Inside your application you may want to show Uniqs (NFTs) which have been marked to be sold by their respective owners.
If you'd like to get this information directly from the blockchain, you can reference the resale.a table within the eosio.nft.ft account.
To quickly view the contents of this table, you can use the Block Explorer: https://explorer.mainnet.ultra.io/account/eosio.nft.ft/tables?scope=eosio.nft.ft&tableName=resale.a