To talk about the modern economy, specialized services, and everyday jobs, you don't always need to learn entirely new words. Polish frequently creates agentive nouns—words for professions and doers of an action—by attaching specific suffixes to existing words.
The classic suffix -arz
The suffix -arz (sometimes spelled -erz) is one of the most common ways to form a profession. It usually attaches to a noun to indicate someone who works with or makes that thing.
For example, from taksówka (taxi) we get taksówkarz (taxi driver), and from stół (table) we derive stolarz (carpenter). It can also attach to verbs, like malować (to paint) becoming malarz (painter).
The specialized suffix -owiec
The suffix -owiec is highly productive in modern Polish. It is typically added to nouns to describe a specialist in a particular field, industry, or concept.
For instance, someone who handles szkolenie (training) is a szkoleniowiec (trainer), and an expert in handel (trade) is a handlowiec (salesperson).
The doer suffix -acz
While -arz and -owiec often derive from nouns, the suffix -acz almost always attaches directly to verbs. It creates a noun for the person performing that specific action, very similar to the "-er" ending in English.
If you know the verb słuchać (to listen), you can easily guess that a słuchacz is a listener. Similarly, poszukiwać (to seek) gives us poszukiwacz (seeker).