What substance makes tape SO sticky!?

Regular scotch tape, clear packaging tape, etc. What substance makes it so sticky??? Is it a glue type substance made of horse hooves (like white glue) or some sort of strange chemical compound?
Please tell me the chemical name and its source (animal, vegetable, mineral, or synthetic substance).

From 3M more than you ever wanted to know about the physics and chemistry of adhesive tapes.

Fundamentals of Adhesion

etc etc and more etc

Sticky stuff on post-it notes, tapes etc are low Tg, uncross-linked polymers . Low Tg (glass transition temperature) means they are soft and want to flow. Cross-linked low Tg polymers cannot flow but are still soft, thus they make good rubbers. Because they are polymers (semi liquid) they dont dry out as they have no solvent. I think post-it notes are made of polymers such as poly(butyl acrylate) if that helps