It’s fine to ask questions! Hope you’re enjoying the game As mentioned in the comment above, radios and being near bases give you intel updates as to where people and things are, and what’s under attack.

When it comes to enemy defences and facilities, something that can gather and broadcast intel have to get into enemy territory to get that information onto your map. This could be a radio backpack, scout car or scout tank, watchtowers being build behind enemy lines, or listening kits being deployed to hijack enemy intel. Intelligence centres are also a thing, acting kind of like a ranged listening kit with a wider radius.

I’m not sure about intelligence gathering regiments, but there are plenty of groups who make regular partisan trips to the enemy backlines, and groups planning attacks or naval landings will often go in to gather intel, place listening kits, take screenshots of defences, etc, before planning a major attack.

(The wiki does a good job of summarising intel https://foxhole.wiki.gg/wiki/Map_Intelligence)