die Agentur
agency
A company or office that provides or arranges certain services for other people or companies.
Eine Werbeagentur hat die neue Kampagne für das Produkt entwickelt.
An advertising agency developed the new campaign for the product.

agency
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agency
A company or office that provides or arranges certain services for other people or companies.
Eine Werbeagentur hat die neue Kampagne für das Produkt entwickelt.
An advertising agency developed the new campaign for the product.

The word 'Agentur' (agency) is very often used as the second part of compound nouns. The first part then describes exactly what service the agency offers.
Er hat sich bei einer Partnervermittlungsagentur angemeldet.
He registered with a matchmaking agency.
When it is a company, you can 'beauftragen' (commission/hire) an agency in order to receive a service. You can also work 'für' (for) or 'bei' (at) an agency.
Wir haben eine professionelle Agentur mit der Gestaltung der Webseite beauftragt.
We hired a professional agency to design the website.
State institutions can also be called 'Agentur' (agency). The best-known one is the 'Agentur für Arbeit' (Federal Employment Agency), which is responsible for job placement in Germany.
Wenn man arbeitslos wird, muss man sich bei der Agentur für Arbeit melden.
If you become unemployed, you have to register with the Federal Employment Agency.
company / undertaking
'das Unternehmen' and 'die Agentur' can both refer to an organization that works professionally or offers services. 'Unternehmen' is the general term for an economic organization, for example a company, a business, or a manufacturer. An 'Agentur' is more specific: it arranges or provides certain services, for example advertising, travel, employment, or news. Sometimes an agency can itself be a company. There is a risk of confusion because both occur in business life. If you are talking generally about a company, 'Unternehmen' fits. If it is about arranging services or specific services, 'Agentur' is more precise.

Die Agentur organisiert für unsere Firma eine neue Werbekampagne.
The agency is organizing a new advertising campaign for our company.
Nach der Arbeit besucht Tom ein Unternehmen, das medizinische Geräte herstellt.
After work, Tom visits a company that manufactures medical devices.