Because in the past period of movable type printing in the west, all capitalized fonts were placed on the top of the drawer, so it was sometimes called capitalization.

The height and width of uppercase and lowercase fonts are obviously different, but in some languages, there is no case difference. In the early days of invention, there was only one font for Latin letters, that is, capital letters.

In Chinese Pinyin, China people's and national standards GB/T16159-1996 Basic Rules of Chinese Pinyin Orthography stipulates that proper nouns should be capitalized.

Sometimes, all capital letters help to identify surnames, because languages in different regions have different habits to express names. Esperanto often writes names like this. For example:

George Washington wrote George Washington

Castro writes about fidel alejandro castro ruz

Use of capital letters:

Used at the beginning of a sentence.

Abbreviations.

Increase readability. For example: signs and labels.

In some languages, it has the function of emphasis.

Proper nouns such as names and places.

In German, all nouns start with capital letters, which is the language with the most capital letters.