die Präsenz
presence
The physical presence of a person or thing in a particular place.
Seine Präsenz bei der Konferenz war für das Team sehr wichtig.
His presence at the conference was very important for the team.

presence
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presence
The physical presence of a person or thing in a particular place.
Seine Präsenz bei der Konferenz war für das Team sehr wichtig.
His presence at the conference was very important for the team.

The noun 'Präsenz' (presence) belongs to the word family of the adjective 'präsent' (present). When a person is 'präsent' (present), they have 'Präsenz' (presence/attendance).
Der Chef ist heute im Büro präsent und für alle ansprechbar.
The boss is present in the office today and available to everyone.
You can recognize the meaning from the context. If it is about a place, it means attendance or physical presence. If it is about the effect of a person, it means aura or charisma. In connection with companies or the internet, it refers to visibility.
Ihre Präsenz im Team motiviert alle.
Her presence on the team motivates everyone.
In the sense of 'Anwesenheit' (presence/attendance), the expression 'Präsenz zeigen' (to show presence) is often used. It means to be deliberately present and visible in order to signal support or control.
Die Polizei zeigte auf dem Festival viel Präsenz, um für Sicherheit zu sorgen.
The police showed a strong presence at the festival to ensure safety.
When it is about aura or charisma, 'Präsenz' (presence) is often combined with adjectives such as 'stark' (strong), 'beeindruckend' (impressive), or 'magnetisch' (magnetic). You also say that a person 'hat Präsenz' (has presence).
Trotz seiner leisen Stimme hatte der Redner eine enorme Präsenz im Raum.
Despite his quiet voice, the speaker had an enormous presence in the room.
This meaning is typical in business and marketing contexts. Common compounds are 'Online-Präsenz' (online presence), 'Marktpräsenz' (market presence), or 'Medienpräsenz' (media presence).
Ein guter Online-Shop sorgt für eine starke digitale Präsenz.
A good online shop creates a strong digital presence.
effect / impact
'die Wirkung' and 'die Präsenz' can both describe the impression a person makes on others. 'Wirkung' is more general: it can come from a person, a picture, a speech, or a situation. 'Präsenz' is used especially for people who stand out strongly through the way they are and fill a room or a stage. If you mean the general impression, 'Wirkung' fits. If you mean a strong personal aura or charisma, 'Präsenz' sounds more natural.

Auf der Bühne hatte die Sängerin eine starke Präsenz.
On stage, the singer had a strong presence.
Das dunkle Licht hatte eine ruhige Wirkung auf die Gäste.
The dim lighting had a calming effect on the guests.