Search advertising operates on its own set of mechanics. Quality Score is a platform estimate of the relevance of an ad and its keyword, as well as expected performance, and it affects both ad rank and the CPC an advertiser pays. Ad Rank is the auction score used to order ads on the results page; it is typically a function of bid, quality components, and the expected impact of ad extensions. Together, these signals determine not only position but also cost.
Impression share is the share of impressions an advertiser received out of the total they were eligible to receive, and it is a quick diagnostic for lost opportunity. Impression share can be reduced by budget limits, low bids, low quality, tight targeting, or low ad rank. Improving impression share usually means addressing one of those constraints: raising bids or budgets, lifting quality through better ad relevance and landing pages, or relaxing overly narrow targeting.
Search keywords can be matched to user queries at different levels of strictness. Broad match reaches the widest set of queries, phrase match requires the query to include the meaning or phrasing of the keyword, and exact match is the tightest, though specific behaviors vary by platform and continue to evolve. Negative keywords prevent ads from showing on irrelevant queries, and the search term report, the log of actual queries that triggered an ad, is one of the most useful diagnostics in search: it surfaces new converting queries to add as keywords and irrelevant ones to negate. Ad extensions, sometimes called assets, add extra information such as sitelinks, callouts, and structured snippets, and they tend to improve CTR and overall ad utility.