What exactly do marketing agencies do?
US marketing agencies package the execution of marketing work — strategy, creative, media, content, SEO, social, email, analytics — into services businesses buy instead of hiring in-house. Full-service agencies cover multiple disciplines under one roof; specialist agencies focus on one (SEO-only, paid-only, content-only). Most modern agencies also handle marketing technology setup and reporting. The unifying job is trading their expertise and capacity for your budget.
Why this matters
This question shows up regularly in Google's People Also Ask for the "marketing agency" query, which is a signal that buyers in this space are asking it constantly during their research phase. The answer above is written from The Wall's editorial position — we index 2,286 verified US growth-services vendors across 10 pillars and see how these questions map to actual buying decisions.
If you're evaluating vendors in this category, the Marketing pillar page has the full US firm list with rates, team sizes, and headquarters filters.