I agree. The proper name is TIM (Thermal Interface Compound) but you can't spend all day typing ALL that out.
Thermal Grease, Thermal Compound, Thermal Paste are all used to denote the same thing.
Some heatsinks come with strips of something ready applied. This is Thermal Paste which spreads with pressure and heat. Because it looks new and strange, people have mistakenly removed it and started again!
Even worse, they have added more paste on top of the strips, so it squeezes out of the sides when installed! :?