Explanation
If you meet each of the following prerequisites, you can:
* The ads sets you want to optimize for value are part of a Conversions campaign
* You have a Facebook pixel implemented
* Your pixel has the Purchase Standard Event and it's sending us the value and currency parameters (learn how to set this up, or learn more about standard events)
* Your ad sets are able to deliver consistently (a good benchmark for this is getting about 50 purchase conversions per week per purchase-conversion-optimized ad set)
* Your ad sets send us several different values over the course of the day (ex: someone may buy $10 worth of product while someone else may buy $50). This helps us determine who to show your ads to to generate the most value.

Explanation
The four main factors that affect your ad in an auction are the following:
* Advertiser Bid: How much you value the results you are trying to obtain.
* Estimated Action Rates: How likely Facebook thinks a given person will take action on your ads.
Estimated action rates are based on the person you're reaching historical data and your ad's historical data performance.
* Ad quality: Basically this comes down to your images or creative. The better the ad image, video or design, the more appealing it will be to your target audience; thus, increasing the ad quality.
* Relevance: If ads are getting negative feedback or are not getting actions, your relevance will be much lower.
Ad relevance diagnostics aren't inputs into the ad auction:
* Quality Ranking: How your ad's perceived quality compared to ads competing for the same audience.
* Engagement Rate Ranking: How your ad's expected engagement rate compared to ads competing for the same audience.
* Conversion Rate Ranking: How your ad's expected conversion rate compared to ads with the same optimization goal competing for the same audience.
Facebook uses user value, not any of the ad relevance diagnostics in calculating Total Value. Just keep in mind that the Relevance Diagnostics is an output of all of the metrics above; NOT an input.
Frequency is only a metric as a result of your ads and relationship between reach and impressions.

Explanation
The Facebook main delivery system consists of three aspects:
* Auction: In the Facebook auction, you will be competing against thousands of advertisers worldwide.
They are all competing for one thing. End-users' space on the News Feed, Messenger, Audience Network, Video Ads, and mobile apps. It's just like a normal supply and demand function. The more advertisers competing for your time (demand), the more expensive it will become (supply). So the person willing to pay the most will get most impressions.
* Pacing System: Standard versus accelerated delivery makes a big difference in how your ads perform; especially in costs. Accelerated delivery will underperform your budget but allow you to spend your budget more quickly.
* Advertiser Controls: Obviously the size of your audience, budget, schedule, and type of ads will all affect the delivery of your ads.
Whenever you are running your campaigns, think of those three main areas with how they each will affect running your campaigns in the future.

Explanation
Reach and frequency campaigns have a grace period of 6 hours. After that time, you will have to create a new one and re-launch it as Facebook can't keep your fixed price.