Consent

Definition in the Law art. 4

any freely given, specific, informed and unambiguous indication of the data subject’s wishes by which he or she, by a statement or by a clear affirmative action, signifies agreement to the processing of personal data relating to him or her;

In plain words

Consent is a freely given, specific, informed and unambiguous indication of the data subject’s wishes, by which he or she, by a statement or by a clear affirmative action, agrees to the processing of data relating to him or her. A customer ticking a box to agree to receive offers can amount to consent.