die Verwendung
use
The use or application of something for a specific purpose.
Die Verwendung von Smartphones ist während der Prüfung verboten.
The use of smartphones is prohibited during the exam.

use
Loading your saved state.
use
The use or application of something for a specific purpose.
Die Verwendung von Smartphones ist während der Prüfung verboten.
The use of smartphones is prohibited during the exam.

'Die Verwendung' (use) is the nominalization of the verb 'verwenden' (to use). The ending '-ung' forms feminine nouns from verbs that describe the process or result of the action.
Wir müssen das Material sparsam verwenden.
We have to use the material sparingly.
To say what something is used for, you can use the construction 'Verwendung für etwas haben' (to have a use for something). To say what is being used, the phrase is 'die Verwendung von etwas' (the use of something).
Hast du eine Verwendung für diese alten Gläser?
Do you have a use for these old glasses?
The expression 'Verwendung finden' (to be used) is a more formal way of saying that something 'verwendet wird' (is used). It is often used in written or official contexts.
Dieses Verfahren findet in der modernen Medizin keine Verwendung mehr.
This procedure is no longer used in modern medicine.
operation / effort / use
'der Einsatz' and 'die Verwendung' can be very similar when talking about using something for a specific purpose. 'der Einsatz' often sounds more active or more technical, especially with means, methods, devices, or materials. 'die Verwendung' is more neutral and describes the use of something in general. In many sentences, you can use both words, but the style is slightly different. Learners may confuse them because both mean 'using something'. As a guide: 'Verwendung' is more about the general use, while 'Einsatz' is more about targeted use in a situation.

Zur Verwendung dieses Reinigers braucht man nur wenig Wasser.
You only need a little water to use this cleaner.
Der Einsatz neuer Software spart dem Team viel Zeit.
The use of new software saves the team a lot of time.