Chalav Yisrael (חלב ישראל)

Milk (and dairy made from it) produced under continuous Jewish supervision from the moment of milking — a stricter dairy standard some people prefer.

Long ago the Sages (the early rabbis whose rulings form Jewish law) added a safeguard: milk should be watched by a Jew while the animal is milked, so there's no chance milk from a non-kosher animal gets mixed in. Milk produced with that supervision is called Chalav Yisrael (literally 'milk of Israel'). Milk without it is called Chalav Akum ('milk of a non-Jew').

Regular store-bought milk in a country with strict government food rules (like the USA).

Many people rely on ordinary supervised commercial milk; those who are stricter use milk specifically labeled Chalav Yisrael. Why: Rabbi Moshe Feinstein (a leading 20th-century authority) reasoned that strict government oversight and heavy penalties make it practically impossible for non-kosher milk to be mixed in — so in effect we can all treat it as verified pure cow's milk, which is what the original safeguard wanted.