I2C vs SMBus | Differences & Similarities

I2C (Inter-Integrated Circuit) is an on-board communication protocol that is ideal for short distances and low bandwidth. It has a master-slave architecture in which all slaves are connected to the master via two lines: the serial data line (SDA) and the serial clock line (SCL). I2C is typically used to connect lower speed peripherals such as sensors to processors and microcontrollers over short distances within an integrated circuit.
The I2C protocol defines how data is sent. At the beginning, the master issues a start condition, followed by the address of the slave device with which it is communicating. As soon as the corresponding slave has identified its address, it looks for the progressive read / write flag issued by the master. This flag tells the slave whether it can receive data or send data. As soon as the slave has confirmed the master, communication is continued.
A feature of I2C is the built-in test system: Each data byte is confirmed by the receiver with either ACK or NAK to signal to the sender whether the data has been received or not. As soon as the master has finished communication with the addressed slave, it issues a stop condition to signal the end of the transmission. After the stop condition, communication with other slave devices can begin.