Why is there a white rubbery foam rectangle on fan replacement?

So I purchased a few months ago a fan and heatsink replacement for my Lenovo t480 and since replacing the fan it blows cool air however the fan is really loud still making that loud fan air noise whenever I have my laptop on with literally

nothing running. I bought some thermal paste and went back in to check the fan yesterday and noticed there was a small plastic rectangle sheet on top of a white rubbery rectangle pad that’s attached to the fan replacement they provided me and on top of the sheet was thermal paste but the plastic sheet came off and now it’s just the foam rectangle. Do I need to put on thermal paste on that or is that a thermal pad and I tried running the laptop with just the foam pad and it’s still blowing cool air but still making the loud fan noise when nothings running.