die Halterung
mount / holder
A device or frame used to fasten, support, or hold an object in a specific position.
Ich brauche eine neue Halterung für mein Handy im Auto.
I need a new mount for my phone in the car.

mount / holder
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mount / holder
A device or frame used to fasten, support, or hold an object in a specific position.
Ich brauche eine neue Halterung für mein Handy im Auto.
I need a new mount for my phone in the car.

The noun 'Halterung' (mount/holder) is derived directly from the verb 'halten' (to hold). The ending '-ung' turns it into a thing, namely a device that 'hält' (holds) something.
Diese Halterung hält das Regal sicher an der Wand.
This mount holds the shelf securely on the wall.
'Halterung' (mount/holder) is often the second part of compound words that describe the purpose more precisely. Typical examples are 'Wandhalterung' (wall mount), 'Handyhalterung' (phone mount), or 'Fahrradhalterung' (bike rack/bike mount).
Die neue Wandhalterung für den Fernseher war einfach zu montieren.
The new wall mount for the TV was easy to install.
To describe which object the mount is intended for, you almost always use the preposition 'für' (for) followed by the accusative.
Ich habe online eine Halterung für mein GPS-Gerät bestellt.
I ordered a mount for my GPS device online.
composure / version / frame
'die Fassung' and 'die Halterung' both have to do with something that holds an object. 'Fassung' is more specific: something is inserted into a frame or a fitted place, for example a lens, a gemstone, or a light bulb. 'Halterung' is more general and means any device that fastens, supports, or holds something in position. The words can be confused because both hold something in place. 'Fassung' fits when a part is inserted exactly into something; 'Halterung' fits when an object is generally fastened or supported.

Am Montag montiert mein Freund eine Halterung für das Fahrrad an der Wand.
On Monday, my friend installs a mount for the bicycle on the wall.
Beim Optiker wurde die neue Linse vorsichtig in die Fassung gesetzt.
At the optician's, the new lens was carefully placed into the frame.