The new "Achievements" display, available in "Creator Mode" in the app, assigns various badges to engagement milestones-100 total post likes, 1,000 video plays, and more.
The new "Achievements" will only be accessible for those who have transitioned to a Creator Account. It will appear in the "Your Tools" section of the "Professional Dashboard".

Based on this, according to Instagram, creators will be rewarded with various badges of different levels based on the following criteria:

Post Likes
Reels Plays
Accounts reached with Stories
Follower Count
Lifetime number of Posts
Lifetime number of Reels
Lifetime number of Stories
Other special Achievement badges also include:
Collaborating with other creators by using Instagram Collabs or even remixing a reel
Utilizing interactive stickers with your reel, such as Add Yours sticker, polls, quizzes or questions 
Using trending audio or effects with your Reel
Posting more than one reel in a week
So basically, Instagram's trying to lure more creators to keep posting more often, by giving them a made-up achievement badge, which is meaningless but will probably give you a little shot of dopamine for reaching these milestones with your content.

Will that work? Probably.

Snap Streaks is probably the most evident example that comes to mind, which has close to become a religion for many Snap users over the years. For a Snap streak to be initiated, you and a friend have to send a Snap to each other every 24 hours for three days and then continue to send reciprocal Snaps each day to maintain the streak.

Some Snap users have been holding 6-year-old streaks (and counting), and this compulsion has kept many coming back to the app.

In-app gamification like this, therefore does work, and as such it would not be surprising at all to see these rewards become something that spurs creators in the app.

It's a little less different in that respect, considering the fact that creators have to post content in order to realise these objectives. However, for some it might be that kick one needs to push through, especially in the initial stages when they might not be getting the attention they deserve.

Instagram worked on this feature for over a year, and a test version had first surfaced back in October. Now, with the holidays coming up, it seems to have decided to release the new awards to even more accounts so they wouldn't slow down content during the end time of the year.

It will be interesting to see whether creators actually care, and how this form of gamification drives activity, or not.

Instagram says the feature isn't available in all regions yet, but it will likely see a wider roll-out over time.