When thinking about things being sticky or slick it's useful to think of the molecules as tiny little robots with magnetic grabber arms. Some materials have lots of arms and connect to each other well. Some materials have very few arms and don't have a strong connection. Some materials have the wrong kind of connectors for each other and don't have a connection at all, in fact they push each other apart.
Sticky things like tape, glue, snot and honey are all made up of little parts, molecules, that have a lot of grabber arms. They are also really good at getting into all the little nooks and crannies of what it's trying to stick to.
Slick or oily things like grease, lubricants and ice don't grab on to other things as well as sticky things because they have fewer arms and don't do a good job of making contact with the other surface.
This is why pressing on things helps to make them stick better. You are forcing more of the two things to touch, getting into all the little bits of the surface. You also add energy by pressing which can cause things like forcing more grabber arms to activate.