understanding serial commm

comm serial protocols:
1.usart(universal sychronous asynchronous receiver or ttansmitter):
  -common protocol for device to device communication
2.SPI(serial peipheral interface):
  -short distance communication(faster than usart)
3.I2c(inter-intergrated circuit):
  -allows multiple slave digital ICs to communicate with one or more master chips.
4.USB:widespread standard for connecting devices to computers