What The Changes Are
Facebook moved all the settings you could previously set on an ad level over to the ad set level. In particular, you will now no longer be able to set audience, placement and pricing per ad - instead, you will be able to set them per ad set.
Note: When this change rolls out might vary from one account to another.
Settings for ad sets that are set up after October 17th, 2014, look like this:
What You Could Do Before The Change
Before this change, you could have different settings for a variety of ads within the same ad set.
How Things Work From Now On
Ads with different settings have to be in different ad sets if they are newly created after October 17th, 2014. So you have two options from now on:
What Happened To Your Existing Ad Settings
Everything you created so far stays the same. Since today, you can no longer set your settings at the ad level and all ads that are created from now on will have to be sorted into ad sets based on their settings as described above.
Why This Matters To Advertisers
This change has a big impact on how Facebook campaigns are structured. Instead of creating ad sets that each have a set of ads about the same topic, ads can now be about different topics as long as they have the same settings. This change goes well along with Facebook's best practices of segmenting your account structure as much as possible.
A concrete example: let's assume we have two audiences.
Audience 1: one with ages 20-30 and an interest in tennis
Audience 2: one with ages 30-40 and an interest in golf
Your options would be the following.
If you set it up before October 17th:
If you set it up after October 17th:
For advertisers who want to keep things separate, the workload will double. Additionally, the way Facebook campaigns are structure from now on will be different from existing structures and therefore the existing structures must be adapted or the account will end up having two different setups.