Why do you salt pasta water, and does it make it boil faster?

Salt in pasta water is about seasoning, and it is the only opportunity to season the pasta itself rather than just what goes on it. Pasta absorbs water as it cooks, and salted water means it absorbs seasoned water, producing pasta that tastes like something on its own. The usual guidance is water that tastes noticeably salty, often cited as roughly one to two tablespoons per gallon, and most of that salt stays in the water and goes down the drain rather than into the food, which is why the quantity sounds alarming and is not.

Two adjacent myths deserve correcting. Salt does not make water boil faster; dissolved salt raises the boiling point slightly, meaning salted water must get marginally hotter before it boils, and at culinary quantities the effect on both boiling point and timing is negligible either way. And adding oil to the water to prevent sticking does not work, since oil floats and the pasta is underneath it, while the oil that does coat the pasta on draining makes sauce slide off rather than cling. Stirring in the first minute prevents sticking. The genuinely useful trick most home cooks skip is reserving a cup of the starchy cooking water before draining, since the dissolved starch emulsifies with fat to bind sauce to pasta, which is the actual difference between restaurant pasta and a bowl of noodles with sauce sitting on top.