Reach is the number of unique individuals who saw a particular post or piece of content - regardless of how many times they saw it. It differs from impressions, which count total views including repeats. Reach is a measure of how many distinct people your content actually got in front of.
Reach can be broken down into organic reach (unpaid distribution), paid reach (from ads or boosts), and viral reach (people who saw it because a friend shared it). Growing reach is a core goal for brand awareness campaigns, while marketers focused on conversion tend to care more about whether the right people were in that reach figure.
