It means that the customer's consent to receive, for example, newsletters on the general terms and conditions of the GTC right. §§ 305 ff. BGB. Thus, a wording "you will receive interesting offers" for the description of the subject of future newsletters according to § 307 para. 1 S. 2 BGB would be ineffective, since customers can not recognize this, what is the advertising.
Another example of an inadmissible consent to the receipt of advertising, the OLG Cologne with judgment v. 23.11.2007, Az .: 6 U 95 / 07 seen in the following formulation:
In the present case, the point was that a company wanted to use the customer data of its raffle participants for other purposes, which have nothing to do with the actual raffle. Such a coupling violates several laws. For example, against the coupling ban of the DSGVO.
You should therefore check your texts for the approval of newsletters or present them to a law firm specializing in IT law.