What, precisely, is "fog of war"?

[Ian Boys]

It allows some enemy icons to appear in an otherwise no icon server.

For example - you are flying an IL-2 and a Pe-2 recon ahead of you flies over some blue tanks and reports them back.

Example 2 - you have a radar unit at your base and enemy up to 30km away over 40m alt (for example) show up on your map. However their position updates only every 30 secs. So it give you an idea what is close but not completely realtime.

It is great - you know things you would know and don't know things you wouldn't know.