Search Ads are paid text ads that appear in search engine results pages (SERPs) when users search relevant terms. They are the most effective format for capturing existing demand because they target people with active buying or research intent. They work on a CPC (pay-per-click) model.
When someone searches 'digital marketing agency London', your ad appears in the top 3-4 positions of the Google page, above organic results, with call, location, and sitelink extensions.