der Lappen
rag / cloth
A piece of cloth used for cleaning, wiping, or drying.
Kannst du mir bitte einen nassen Lappen geben, um den Tisch abzuwischen?
Can you please give me a wet cloth to wipe the table?

rag / license / wimp
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rag / cloth
A piece of cloth used for cleaning, wiping, or drying.
Kannst du mir bitte einen nassen Lappen geben, um den Tisch abzuwischen?
Can you please give me a wet cloth to wipe the table?

This word has four very different meanings. The context makes it clear whether it refers to a cleaning cloth (neutral), a driver's license (colloquial), an insult (derogatory), or a medical term (technical language).
Gib mir bitte den Lappen, ich habe etwas verschüttet.
Please give me the cloth; I spilled something.
In the meaning 'Putztuch' (cleaning cloth), the word is often combined with verbs related to cleaning. Typical phrases are 'etwas mit einem Lappen abwischen' (to wipe something with a cloth), 'einen Lappen auswringen' (to wring out a cloth), or 'einen Lappen benutzen' (to use a cloth).
Wisch bitte den verschütteten Kaffee mit einem feuchten Lappen auf.
Please wipe up the spilled coffee with a damp cloth.
The term 'der Lappen' for a driver's license is very common, but purely colloquial. You often hear it in connection with the verbs 'abgeben' (to hand in), 'verlieren' (to lose), 'machen' (to get), or 'wegnehmen' (to take away).
Wegen zu schnellem Fahren ist er seinen Lappen für einen Monat los.
Because of speeding, he lost his license for a month.
Calling someone a 'Lappen' (wimp) is a colloquial insult. It describes a person who is seen as weak-willed, cowardly, or boring.
Trau dich endlich und sei nicht so ein Lappen!
Finally have the courage and don't be such a wimp!
In medicine or biology, 'Lappen' (lobe) refers to a separated part of an organ. This use belongs to technical language and is not used in normal everyday speech.
Der Arzt erklärte, dass der rechte Lungenlappen entzündet ist.
The doctor explained that the right lung lobe is inflamed.
driver's license
'der Führerschein' and 'der Lappen' can both refer to the document that allows you to drive a car. 'Führerschein' is the normal and neutral word, especially in government offices, traffic stops, or driving tests. 'Lappen' is colloquial and often a bit casual or derogatory. Learners may confuse the words because, in this meaning, 'Lappen' really does mean 'Führerschein'. In official situations, however, you should always say 'Führerschein'.

Nach drei Fahrprüfungen hat Tom endlich den Lappen bekommen.
After three driving tests, Tom finally got his license.
Bei der Polizeikontrolle zeigt Max seinen Führerschein.
During the traffic stop, Max shows his driver's license.