No. Peanut butter is, at its most basic, ground peanuts (sugar or salt is sometimes added). The consistency, creamy and suggestive of butter, is actually due to the peanut solids being in suspension...
No, peanut butter and butter are very different things. They don't substitute for each other. While peanut butter is thick and sweet , and butter is not thick , and salty , they are almost opposites .