When TikTok sends you a notification that someone "you interacted with" posted a video, it generally means that you have engaged with that user's content in some way in the past. The notification is intended to draw your attention to the fact that they have uploaded a new video, as TikTok's algorithm assumes you may be interested in seeing it based on your previous interactions.
The types of interactions that can trigger this notification include:
Likes: If you've liked one or more of their videos in the past, TikTok may notify you when they post a new video.
Comments: Leaving comments on a user's videos can also count as an interaction, prompting TikTok to send you a notification when they upload new content.
Follows: If you follow a user, it is considered an interaction, and you may receive notifications about their new videos.
Duets and Reactions: If you've done a duet or reaction video with them, TikTok will notify you when they post new videos.
Shares: Sharing a user's video can also be considered an interaction, resulting in notifications when they post more content.
It's important to note that TikTok's notification system is driven by its algorithm, which aims to keep users engaged with the platform by showing them content they are likely to enjoy. As a result, the "you interacted with" notifications are part of TikTok's effort to personalize and curate your content feed based on your past activity and interests.