Removable Adhesive:

A removable adhesive is a lower-tack adhesive that is designed to remove cleanly. It is less likely to remove paint from the surface or leave sticky residue behind. Generally, vinyl with a removable adhesive can peel off the surface with minimal force.
A common misconception is that the term "removable" means that the adhesive will stop working at some point. That is not true, the term is related to the tack and residue factor.

Permanent Adhesive:

A permanent adhesive is a higher-tack adhesive (than removable) and more likely to leave adhesive residue behind if the vinyl is ever removed.
It is recommended to use heat when removing vinyl with a permanent adhesive. Heat gun or even hair dryer would do the trick.

Source: Orafol America