Real-time multiplayer games must constantly keep each player’s view of the world in sync with the authoritative game server.
This is one of the hardest challenges in networked game development because:

• Networks introduce latency
• Packets get lost or delayed
• Input arrival times differ
• Players have unpredictable connections
• Tick rates differ between client and server
• Bandwidth is limited (especially mobile)

State synchronization (“netcode”) is the art of making every player experience smooth, fair, and consistent gameplay, despite these constraints.