A case may refer to any of the following:
How to change the case
To change the case of a letter, press and hold down the Shift key, then press the letter you want to be capitalized. Or, turn on the caps lock feature by pressing the Caps Lock key to make all letters capitalized.
What is sentence case?
Sentence case is the capitalization of the first word of the sentence with all other letters being lowercase, like this sentence. If the sentence contains proper nouns (names, companies, and places), titles (e.g., books, magazines, and movies), or acronyms should be properly capitalized.