An alphanumeric keypad is a keyboard that contains both numbers and letters on the same keys. Typically, they are found on telephones and cellular phones. They also can appear on laptops, ATMs or any device where both numbers and letters are equally necessary. On phones, the number "1" is typically devoid of any letters; each of the other keys contain only three letters in alphabetical order.
Telephones and cell phones use nearly identical alphanumeric keypads. The only difference being that most telephones lack a "Q" and a "Z", whereas cell phones require the alphanumeric keypad for texting and have added these letters back into the keypad. One cell phones, there is also often a key used for creating a "space" as well as another number that is used for punctuation or capitalization.
Most laptops, in an effort to save space, remove the typical numeric keypad present on a traditional keyboard. Some manufacturers have opted to include it within the letter portion of the keyboard with an extra button press (a "function" key) required to use it as such. The keys are usually labeled with superscripted numbers in an alternate color.
Automated teller machines (ATMs) found at banks and some businesses, have an alphanumeric keyboard for the sake of personal identification numbers (PIN). Instead of remembering only numbers, some people link a word to their PIN based on the letters available on the corresponding numbers of their PIN.
They alphanumeric keypad has become quite commonplace and is generally found wherever numeric keypads are used: gas pumps, debit card readers, mp3 players, jukeboxes, etc. The letters are usually clearly labeled on each key and either start on number 1 or 2.