Industrial PCs are computers meant to go in industrial environments. They vary quite a bit but often have to handle dirty (possibly explosive or corrosive) air, 24v power, wide temperature ranges, lots of electrical and radio noise, and being cabinet mounted.

If you've got a little Node-RED box reading serial data from your bar code reader, doing lookups in your SAP database, and then sending Modbus commands to your PLC to redirect a box down a different conveyor line, it's probably an industrial PC.