Re: Can someone explain what polyurethane is for?
Yes, you need to apply a finish. Pine is a softwood and wears easily. The stain doe not protect the floor from wear. I only use OldMasters brand poly. It is easy to apply because it has very good self leveling properties and dries to a hard durable finish. You have the choice of either and oil based or a latex based poly. The latex based poly is clearer but not quite as durable the oil based will add a slight amber tint to the finish but is more durable. The self leveling properties means that it hardly shows brush marks. You should apply a minimum of 3 coats.
Be sure you live your life, because you are a long time dead.-Scottish Proverb