Here's a breakdown:

* Selectivity: Channels are designed to allow only specific types of molecules to pass through. This selectivity is based on factors like size, charge, and chemical properties of the molecule.

* Movement: Channels facilitate the movement of molecules across the membrane, which can be either passive (down a concentration gradient) or active (requiring energy).

* Examples: Examples of channels include ion channels (for ions like sodium, potassium, and calcium), aquaporins (for water), and glucose transporters (for glucose).

Let me know if you'd like to dive deeper into specific types of channels or their functions!