This is the standard zipper type. There is a hollow cavity on the zipper which you must put your finger into to open the package.

It cannot be opened like the average package by simply pulling, unless great strength is applied. These two features make the package child-resistant.

This tab type is the easiest for adults to open. There is a tab on the zipper which you must hold while opening to open the package.

It is difficult for children to hold the tab while trying to open the package, making it child-resistant.

This slider type is the most commonly used type in the US. Move the slider onto the cavity and press down on the slider while pulling it to the opposite side to open the package.

Since it is difficult for children to imitate the process of holding down the slider, and because a degree of strength is required, the package is child-resistant.