From an Italian - English dictionary

Agenzia can mean either "agency" or "branch office." A lot of new companies that are formed are some type of agency. For instance, there are advertising agencies and talent agencies.

In English, an agency is a business or organization created to provide a specialized service. Typically they act as a middleman between two businesses. An advertising agency works to connect a company with their consumers. A talent agency works to connect talent, whether it's sports talent, acting talent or musical talent, with a team, casting director or record label.

There are also government agencies, some of them even affect new companies and business filings. These might be taxation agencies, revenue agencies or licensing agencies. If you're starting a new company, you're probably going to get tired of seeing and hearing the word agency.