In order to obtain contact information from an individual, and therefore create an Audience Profile, you must have their consent. This consent must be freely given, specific, informed and unambiguous; meaning that when individuals provide you with their information they must do so being aware of its purpose.
Individuals can provide and withdraw different types of consent, in various levels.
Profiles' consent can be generally divided in two different statuses, and this is often enough to understand whether a Profile will or will not receive your communications:
Opt-in: Subscribed, provided consent.
Opt-out: Unsubscribed, withdrawn consent.