A waiver is something you must agree to in order to participate. For example, a common waiver is the release of information to medical personnel in an emergency. Waivers appear on the final step, and must be checked off in order to share your or your dependent's record with an organization.
A consent is something you can agree or disagree with, and still be able to participate. For example, a common consent is a photo release question, where you can say yes or no to the use of your picture. Consents appear in the second to last step, and either a yes or no must be selected.