Even pacing: Impressions will be paced out evenly throughout the day. 
ASAP pacing: The campaign will attempt to spend the daily budget as quickly as possible. This will double your bid price and may cause your Line to pace ahead of schedule. Because ASAP pacing will remove the performance focus of the campaign, we only recommend using ASAP pacing for campaigns that are extremely behind on budget and/or nearing the end of the campaign, or for single-day campaigns.