Uppercase refers to the larger form of letters used in writing and typography. These letters are typically used at the beginning of sentences, for proper nouns, and for emphasis. For example, the letter A in uppercase is written as A, while its lowercase counterpart is a. In digital communication, uppercase letters can convey shouting or strong emotions. Many computer keyboards have a "Shift" key that allows users to type uppercase letters easily. Additionally, uppercase letters are often used in titles, headings, and acronyms, such as NASA or UNESCO, to signify importance or distinction.