SERP
A SERP is a search engine results page. In lead generation it matters as a data source: the organic results for a query like "orthodontist Lyon" are a list of businesses in that category and place.
Search results reach businesses that never claimed a map listing and never joined a directory, which makes them genuinely complementary rather than duplicate. A business with a good website and no Maps presence is invisible to a Maps-only tool and obvious to a search-based one.
The trade-off is precision. Map results are structured — every row is definitely a business, with a category attached. Search results are pages, and a fair number will be directories, news articles and competitors rather than the businesses themselves, so extraction has to filter harder.