
der Drücker
door handle
The handle on a door that you press down to open the door; a door latch or handle.
Der Drücker klemmt, ich bekomme die Tür nicht auf.
The door handle is stuck; I can't get the door open.
door handle / button / pushy salesman
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door handle
The handle on a door that you press down to open the door; a door latch or handle.
Der Drücker klemmt, ich bekomme die Tür nicht auf.
The door handle is stuck; I can't get the door open.

button
A button on a device that you press to trigger a function, for example the shutter release on a camera or a stopwatch.
In dem Moment, als der Vogel aufflog, betätigte sie den Drücker ihrer Kamera.
At the moment when the bird flew up, she pressed the button on her camera.

pushy salesman
Colloquial and derogatory for a person who tries to sell contracts or subscriptions in an intrusive way at the front door or on the street.
Gestern war schon wieder ein Drücker da, der mir ein Zeitschriften-Abo aufschwatzen wollte.
Yesterday there was yet another pushy salesman who wanted to talk me into a magazine subscription.
'Der Drücker' is derived from the verb 'drücken' (to press). The ending '-er' here refers either to a tool used for pressing (door handle, button) or to a person who does something (here: pressures someone).
Ich habe den falschen Drücker an der Fernbedienung erwischt.
I hit the wrong button on the remote control.
The context makes clear which meaning is intended. On a door, it is the handle; on a device, it is the button; and when it refers to a person who wants to sell something, it means the pushy salesman.
Der Drücker an der Haustür ist kaputt.
The door handle on the front door is broken.
In connection with a door, the most common action is 'den Drücker herunterdrücken' (to press down the door handle).
Man muss den Drücker fest herunterdrücken, um die alte Tür zu öffnen.
You have to press the door handle down firmly to open the old door.
In the meaning 'aufdringlicher Verkäufer' (pushy salesman), the word is colloquial and has a clearly negative, derogatory meaning.
Meine Oma hat sich von einem Drücker ein teures Zeitungsabonnement andrehen lassen.
My grandma was talked into buying an expensive newspaper subscription by a pushy salesman.
switch / counter
Schalter and Drücker can trigger an electrical function. A Schalter is typically used to switch between states such as on and off. A Drücker is pressed briefly so that the device performs a single function.

Mit dem Drücker startet Tom am selben Gerät einen kurzen Test.
Tom uses the button on the same device to start a short test.
Mit dem Schalter schaltet Tom das Gerät dauerhaft ein.
Tom uses the switch to leave the device turned on.