Strongholds are what your Eyes of Ender are actually pointing at, and there are exactly three rings of them around the world origin. Drop a seed in and the map marks every stronghold it finds, so you can see the nearest one and its coordinates before you burn a single eye.

• The innermost ring sits roughly 1,280–2,816 blocks from the world origin — not from your spawn point, which is why the closest stronghold is often not the direction you expect.
• Every stronghold has one End portal room. Finding the structure on the map does not tell you how many portal frames already hold an eye — that part is still a surprise.