The CPM is the Cost Per Thousand Impressions. As an advertiser you will pay Facebook / Instagram every time your ad is viewed 1000 times.

CPM is determined by the auction competition and the ad quality.

There are two main reasons for higher CPMs:

1. High Demand: If there is a lot of competition for the same target audience, the cost of advertising can increase (also during times of high demand, such as during holiday shopping seasons, summer, end of year, the CPM is likely to be higher).

2. Specific Target Audience: If your target audience is highly segmented and specific, there may be less inventory available and the cost of reaching that audience may be higher.

Advice: If your CPM is to high you should check and to increase the budget or make the audience more open.