Final answer:
Chemotaxis is the process where cells move towards a higher concentration of a chemoattractant, whereas diffusion involves the passive movement of substances from a high to a low concentration area until equilibrium is achieved.
Step-by-step explanation:
When migrating cells move toward a greater concentration of a diffusible chemical, the chemical is called a chemoattractant. This process is known as chemotaxis, which is the directional movement of a cell in response to a chemical attractant. On the other hand, organisms that obtain their energy from the transfer of electrons originating from chemical compounds are called chemotrophs. It is important to note that diffusion is a passive process where substances move from an area of higher concentration to an area of lower concentration until equilibrium is reached. This passive transport requires no energy expenditure and is driven by the concentration gradient across a permeable membrane.