If your institute uses this feature, you may be asked to sign a contract during registration or on first login, most often a terms-and-conditions or cancellation-policy agreement. It can also be used for more than a plain legal agreement: some institutes combine it with separate, individually-worded consent questions on the same document (for example, agreeing to the cancellation policy and, as a distinct checkbox, consenting to your child's name or photo being used in testimonials or marketing). You'll receive an email asking you to sign; selecting the link in that email takes you straight into the platform to review and sign it there.
Whether it's the parent or the student who signs is set by your institute as a single global setting, not chosen per document or per question. Many institutes with younger students restrict this specifically to the parent or guardian, since a minor generally can't be the one to sign it in a legally binding way.