This is the "Pin file" or "pins file", in .qsf format, for the Altera DE1 FPGA. It is used to let the Quartus II software know how to route the pins for this model of FPGA.
The support and documentation for this old FPGA has disappeared progressively from the internet, specially since Intel bought Altera. And this file became more difficult to find. If you want to use an Altera DE1 FPGA you probably need this pin file.