Profibus is a standard for field bus communication promoted by Siemens. Two variants are commonly used today.
Profibus PA (Process Automation) is used in process automation applications and is suitable for explosion/hazardous areas limiting current it supplied to field instruments so that explosive conditions cannot happen under error conditions.
Profibus DP (Decentralized Peripherals) is used in factory automation to provide a higher speed network for process signals to sensors and actuators often via a centralized PLC. It uses the same protocol as PA allowing the two network types to be connected via a coupler.