CPU is a time-denominated resource in EOS network. CPU measures the amount of time an EOS BP should dedicate to transactions from your account. In simple terms, the CPU is like a processor in a computer. The more transactions there are in EOS network - the more CPU will be needed. Thereby, the EOS CPU cannot be traded or sent to another account after receiving. On CODEX EOS CPU can be delegated only for 3 days. After the end of this period exchange will un-delegate provided amount of EOS.
Attention! Do not request CPU AID for an exchange addresses. Please, request it only for personal EOS accounts, otherwise, it will not work.