Alphanumeric refers to a combination of letters and numbers. It includes the 26 letters of the English alphabet (A-Z, both uppercase and lowercase) and the digits from 0 to 9. This type of character set is commonly used in passwords, usernames, and various coding systems to enhance security and ensure a wider range of possible combinations. In computing, alphanumeric characters are essential for data entry and programming. For example, in HTML and JavaScript, alphanumeric strings are used to define variables and create identifiers. This versatility makes alphanumeric characters crucial in many digital applications, including databases and online forms.