fvp is just an extension. You have a text file. It looks like the name of the program may be FVParticles, maybe v2.1. The extension is just an easy way to identify that it is an output file from that program.
It looks like the file has 0 Tag name, and 2 variable names, paricle id and particle_id.
I am guessing the 321 may be the number of data points.
You've got five columns of data. The last 2 are probably all 0 and can be ignored, as they may be place holders for additional unused variables. I don't know if the first column is X values or not.
You can use Excel to plot the data. Import the text file into Excel and then plot the 3 columns of data. You can try plotting each as a seperate plot on the graph, or use the first column for the X values and the 2nd and 3rd as the y values (this is probably how it is supposed to be done). If you don't know what the data is, then you will have a hard time knowing if you are plotting it correctly.
