What does John 11:10 mean?

Here Jesus contrasts the idea of those who walk according to the knowledge of God—"walk[ing] in the day"—with those who ignore or rebel against God. His disciples are concerned because Jesus intends to travel back into Judea, close to the religious leaders who want Him dead (John 11:7–8). What they do not know is that Jesus means to resurrect Lazarus, providing yet another sign of His divine power (John 11:1–4, 41–44).

In the prior verse, Jesus spoke of the need to "walk in the day," since that light allowed a person to travel safely. Here, Jesus contrasts this with walking in the night. The lack of light presents danger—a person cannot see the path, or obstacles, or other hazards. This follows a common metaphor used in the Bible, where light represents the will and knowledge of God.

In short, Jesus is reminding His disciples that following God is always the "safest" course of action, even when the world sees it as foolish or dangerous. That's not to say that following God's will keeps Christians from all possible harm. Quite the opposite; obedience to Christ can result in persecution and death (John 16:1–2). Rather, it means that God is in control, and our most beneficial choice is to follow His lead. He'll provide as much protection as His will requires.