To provide consent is to actively provide permission or agree to something. The more specific term "informed consent" is used to emphasize that in order to provide such permission, a person must be provided clear and correct information (not deception), and be able to comprehend such information. In the context of a research study, per The Belmont Report guidelines, a person must also be informed of their right to volunteer or not to participate in the study, and of their right to withdraw from the study at any point. Ideally, consent would also be enthusiastically given (see The Belmont Report page; also see this image from Planned Parenthood that reads "CONSENT: I [heart] FRIES: Freely given, Reversible, Informed, Enthusiastic, Specific."
