Diffusion:
Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration. It occurs due to the random movement of particles and does not require any external energy input. Diffusion is a passive process and is driven by the concentration gradient of the substance.

Facilitated Diffusion:
Facilitated diffusion is a type of passive transport that allows the movement of specific molecules across the cell membrane with the help of transport proteins. It also occurs from an area of higher concentration to an area of lower concentration, similar to simple diffusion. However, facilitated diffusion requires the presence of specific transport proteins to facilitate the movement of molecules across the membrane.

Differences between Diffusion and Facilitated Diffusion:

1. Mechanism:
- Diffusion: In diffusion, molecules move directly through the lipid bilayer of the cell membrane.
- Facilitated Diffusion: In facilitated diffusion, molecules move across the cell membrane with the assistance of specific transport proteins.

2. Energy Requirement:
- Diffusion: Diffusion is a passive process that does not require any energy input.
- Facilitated Diffusion: Facilitated diffusion is also a passive process that does not require energy input.

3. Rate of Transport:
- Diffusion: The rate of diffusion depends on the concentration gradient, temperature, and size of the molecules.
- Facilitated Diffusion: The rate of facilitated diffusion is influenced by the number of available transport proteins and their saturation level.

4. Specificity:
- Diffusion: Diffusion is a non-specific process and allows the movement of any molecule that can pass through the lipid bilayer.
- Facilitated Diffusion: Facilitated diffusion is a specific process and only allows the movement of specific molecules that can bind to the transport proteins.

5. Examples:
- Diffusion: Examples of diffusion include the movement of oxygen and carbon dioxide across the respiratory membrane and the movement of small lipid-soluble molecules through the cell membrane.
- Facilitated Diffusion: Examples of facilitated diffusion include the transport of glucose, amino acids, and ions across the cell membrane.

Overall, while diffusion and facilitated diffusion both involve the movement of molecules from an area of higher concentration to an area of lower concentration, facilitated diffusion requires the presence of specific transport proteins and exhibits higher specificity compared to simple diffusion.