Trueview is YouTube's opt-in skippable ad format where advertisers only pay when viewers watch an ad for at least 30 seconds or until completion if the ad is under 30 seconds. Trueview campaigns are set up through the AdWords interface and allow advertisers to target audiences and control settings like daily budget, cost per view bid, and ad formats. Key metrics for Trueview include view rate, impressions, views, average cost per view, and view-through conversions to measure brand awareness and consideration over direct sales.