The player's position, as they move around, can become de-synced on the server when compared to what the client sees. Ideally, these positions should never become separate and should remain the same.
- Download and import the attached MCWorld file, and open the world in-game.
- Go over to the command blocks and hit the button to activate them. You should see a message in chat stating the dots are enabled, and there should be two colored dots beneath you. The red dot represents where the client says you are, while the aqua dot represents where the server says you are.
- Walk around, and try turning your camera at the same time. The aqua dot should start veering away from where the red dot is.
- Continue to offset the two positions. After the server position moves too far, it should snap right back to where the client position is.
- Try teleporting yourself to yourself: /teleport @s @s or /teleport @s ~ ~ ~. This will place you where the aqua dot is.
- Displace the two dots, then try walking against the corner of a block. The server position expects you to move one way, when the client says otherwise, so they move out of sync.