Umlauts are diacritical marks used in the German language and some other languages to modify the sound of vowels. They appear as two dots above the letters a, o, and u, transforming them into ä, ö, and ü. This change alters the pronunciation, making it distinct from the original vowel sounds. In addition to German, umlauts can also be found in languages like Hungarian and Turkish. They serve a similar purpose, indicating a change in vowel quality. Understanding umlauts is essential for proper pronunciation and comprehension in these languages.