The difference between consent and assent is that:
consent can only be given by the participant.
assent is given by someone who does not have the ability to give consent themselves.
assent can only be given by a parent or legal guardian on behalf of the participant.
consent is given by someone who does not have the ability to give assent themselves.

The difference between Consent and Assent is that, Assent is given by someone who does not have the ability to give consent themselves.

Explanation:

Consent itself is defined as the permission or agreement by a person or individual who has reached the age considered to be adult, or age termed as "legal age" (in most countries, this is usually 18years or 21years) to the proposal, want, desire or request of another.

While, Assent is defined as agreement to a proposal of another person, of which the person agreeing or giving assent to the proposal is not able to give "legal consent" due to age; having not reach the "legal age" at the time.

However, for Assent to be binding on the child or minor, in a legal or contract situation, it requires that the parent or legal guardian gives consent as well.