Here's why:

* Movement across the cell membrane: This indicates that substances are moving from one side of the membrane to the other.

* Made possible by a protein embedded in the membrane: This means the movement isn't happening directly through the phospholipid bilayer, but with the help of a membrane protein.

* Facilitated diffusion: This is a type of passive transport where a membrane protein helps move substances across the membrane down their concentration gradient (from high concentration to low concentration). This process doesn't require energy.

Examples of facilitated diffusion:

* Glucose transport: The protein GLUT4 facilitates the movement of glucose into cells.

* Ion channels: These proteins create specific pathways for ions (like sodium, potassium, calcium) to cross the membrane.

Let me know if you'd like more details about facilitated diffusion!