While many home cooks finish their pasta on a plate or bowl by adding the sauce, the best possible results for the dish come from cooking it together in a saucepan.
The water carried over from the pasta and into the pan contains starch from the cooked noodles, allowing for a thicker sauce that can better adhere to the food.
To get the most out of this hack, it's best to simply scoop your pasta directly from the pot of water and into your saucepan rather than rinsing or draining your pasta.