Reach is the number of potential customers that will be exposed to a message through a particular media vehicle. So, the higher the reach, the larger the number of people that see your message. The higher the frequency, the more times individual people see/hear your message.
What happens after 10k followers on Instagram?
Once you have 10k followers, Instagram will make it easier for you to get people to your website via Stories with the swipe up to link feature. Swipe up is the only way to get a direct link from your Instagram to your other web properties. And, it’s available in STORIES, if you have 10k followers.