A string is a sequence of characters used in programming and computer science to represent text. It can include letters, numbers, symbols, and spaces. Strings are often enclosed in quotes, such as "Hello, World!" or '12345', to distinguish them from other data types. In many programming languages, strings are versatile and can be manipulated through various operations. Common operations include concatenation, which combines two strings, and substring extraction, which retrieves a portion of a string. Strings are fundamental in applications like web development, data processing, and user interfaces.