Instagram's half-swipe allows you to see the content of the next reel without being notified who visited which reels.So if you want to know the process of half swiping on Instagram reels then follow the given steps -
1. Open Instagram on your mobile phone.
2. Open the reel that you want to half swipe.
3. Then, Scroll down slowly until you reach the next reel.
4. Look for a border or a separation line at the end of the current reel.
5. Keep scrolling down until the new reel starts playing, but don't go over the border.

source - https://allinsider.net/how-to-half-swipe-on-instagram/