While the Explore Page is essentially an aggregation of posts that Instagram thinks you’ll like based on your behavior, when you browse a hashtag on Instagram, every Instagram user sees the exact same top posts! It doesn’t matter if you’re in Maui or Madagascar, if you get into the top posts for an Instagram hashtag, anyone who searches for that hashtag will be able to see your post.
If you’ve ever searched for a hashtag on Instagram, you’ve probably noticed the grid of nine «top posts» that appear at the top of the results page.
For example: If you use the hashtag #love in your posts, it will appear to anyone searching for #love, increasing your reach, and chances of likes and new followers.
Hashtags are used to categorize the posts, they create a dynamic interaction with users that aren't your followers, but are interested in the same matter as you.
Like the Explore Page, top posts are chosen algorithmically based on several factors.