ProfiBus is on a 2 wire RS485 platform with different protocol communication layers that actually define ProfiBus. It's widely used in Europe & Asia for industrial applications. Field communication bus, allows you to enhance the number of devices controlled by for example a PLC. It can be described as a serial network were every device connected to it has an ID number, and a range of inputs and outputs, these ranges are normally defined when creating your hardware configuration, and the device or slave number is commonly defined at the device itself using deep switches.
One of the big advantages is that once you have a system defined - everything is saved in the ProfiBus Master. The only thing you have to do if you exchange slaves of the same type is to make sure that the Bus address is correct.
Profinet - now on the other hand side is similar, but with a slightly different hardware platform, it is 4 wires instead of 2 similar to Ethernet, which requires a little bit different System Topologies.