The Schengen Area, explained for first-time visitors

The Schengen Area is a group of European countries that abolished passport checks at their shared internal borders — once you're in, you can generally cross into another Schengen country without a formal border check. Most, but not all, EU countries are members; a few non-EU countries (like Norway, Switzerland, and Iceland) are also part of it, while some EU countries (like Ireland) are not.

For visa-exempt travelers (including US citizens on short tourist trips), the key rule to know is 90 days within any 180-day period across the ENTIRE Schengen Area combined — not per country. Overstaying can result in fines or future entry difficulties, so it's worth tracking your days carefully if you're combining multiple European trips close together.