We've been doing it wrong all this time
Ok but what is it? :/
That is a thermal paste which you apply ON TOP of your CPU, BETWEEN your CPU and its heatsink.
In that gif the thermal paste is being applied into the CPU socket and then the CPU itself follows. If you did that, you could throw your motherboard and CPU into the trash bin.
Literally gore. I'm going to trigger so many people with this gif later, thanks!