What is the core difference between 'Reach' and 'Impressions' in Facebook Ads reporting?

The core difference between 'Reach' and 'Impressions' in Facebook Ads reporting is that 'Reach' represents the number of unique individuals who saw your ad, while 'Impressions' represent the total number of times your ad was displayed. Reach counts each person only once, regardless of how many times they saw the ad. Impressions count every instance of your ad being shown, even if it was shown to the same person multiple times. For example, if your ad campaign has a reach of 10,000 and 30,000 impressions, it means that 10,000 unique people saw your ad, and on average, each person saw the ad three times.