You define a UTM source to know the platform from which the traffic originated.
When to use UTM tags
Literally, every time you want to track the performance of your channels, you should rely on UTM tags. These scenarios can for example include:
Working with Influencers
Track which influencers bring the most traffic to your website.
Find out where your referrals come from.
Distinguish between entry points (for example profile biography and posts)
See which users opened your link
Test different banner ads you’re using