Hey there @Emmytender,
Thank you for reaching out to us again and sorry for the wait.
I've had a look and found a simple explanation. Apparently, the plastic card or "e-residence title" was introduced in 2011 to enable the use of a uniform ID within the EU. Here is what the BAMF says about it:
"The existing residence permit (adhesive label), the residence card and permanent residence card, and the substitute paper identity card, are superseded by the electronic residence permit in credit card format.
The electronic residence permit has a contactless chip inside the card on which biometric characteristics (photo and two fingerprints), supplementary conditions (requirements) and personal data are stored. In addition, the chip can store electronic proof of identity.
All EU Member States are obliged to introduce the electronic residence permit. The basis for this is EU Regulations no. 1030/2002 and no. 380/2008.
The aim is to design a uniform residence permit for the European Union and, by using biometric data, to increase the connection between the document holder and the document, as well as to protect the cards from being misused. A personal electronic residence permit will be issued for every third-country national."
Before the card was introduced, the residence permit was a sticker in the passport. The BAMF also states that "Existing residence permits in passports and substitute identity papers will remain valid until 31 August 2021 at most."
Does this answer your question? :-)
Please feel free to reach out to us again if you need any further assistance.
All the best,