IOST needs two resources to initiate a transaction: iGAS and iRAM
IGAS is the computational resource occupied by the operation instruction, and iGAS will be consumed every transaction operation. If there is not enough iGAS, the transaction will fail. Like the CPU of EOS system, are mortgage resources with linear recovery.
IRAM is memory, used to store account information, including account balance, public key, pledge, vote, intelligent contract, etc. Usually 1KB~5KB capacity can meet the daily operation requirements, iRAM can be bought and sold at any time.