SE is a CPU card that can run smart card applications (called applets or card applications).
A smart card is essentially a micro-computing environment on a single chip, with a complete CPU, ROM, EEPROM, RAM and I\/O interfaces. General smart cards also have key algorithm coprocessors, which can support common encryption and decryption algorithms, such as DES, AES, and RSA. Smart cards achieve attack resistance through a variety of technologies, and it is difficult to extract data by decomposing or analyzing the chip. In fact, mobile phone users are no strangers to SE, because the SIM card of the mobile phone is itself an SE (technically, it can only be called a SIM card in GSM, and the more general one should be called UICC).