PSP ramping is a firing mode consistent with PSP 2011 rules. Your gun will fire semi-automatically until you pull the trigger at 5 times per second. After that, your gun ramps, which means it fires at whatever the maxed BPS setting you have it on. I believe it bases that firing rate off of the capped firing rate value. I think. Millennium is the same as PSP but you need more pulls per second to activate the ramping. I believe it is 7.5 off the top of my head. Capped firing mode caps your firing rate at whatever you set it for. So even if you are walking your trigger at a firing rate of 10bps and your loader can match, but you have your Etha set to capped mode at 8bps, you will still only fire at 8bps. Uncapped is as fast as you can pull.
If you have your manual, everything you need to know should be in it. I would highly suggest reading it. If you don't, you can download a .PDF version from the Planet Eclipse website.